Varian Solid-State NMR User Manual

User Guide:

Solid-State NMR

Varian NMR Spectrometer Systems

With VNMR 6.1C Software

Pub. No . 01-999162-00, Rev. C0402

User Guide:

Solid-State NMR

Varian NMR Spectrometer Systems

With VNMR 6.1C Software

Pub. No. 01-999162-00, Rev. C0402

User Guide: Solid-Stat e NMR
Varian NMR S p ectrometer Syst ems
With VNMR 6.1C Software
Pub. No. 01-999162-00, Rev. C0402

Revision history:
A0800 – Initial release for VNMR 6.1C software
B0301 – MERCURYplus updates—

cppwr and dblv12 parameters in XPOLAR1

experiment.
C0402 – Updated INOVA CP/MAS parameters for XPOLAR1 and Multipulse

Applicability of manual:
Varian NMR spectrometer systems with
Varian solids modules running VNMR 6.1C software

Technical contributors: Laima Baltusis, Dan Iverson, Dave Rice, Everett Schreiber,
Frits Vosman, Evan Williams
Technical writer: Everett Schreiber
Techni cal editor: Dan Steele

Copyright 2002 by Varian, Inc.
3120 Hansen Wa y, Palo Alto, California 94304
http://www.varianinc.com
All rights reserved. Printed in the United States.

The information in this document has been carefully checked and is believed to be
entirely reliable. However, no responsibility is assumed for inaccuracies. Statements in
this document are not intended to create any warranty, expressed or implied.
Specifications and performance cha racteristics of the software described in this manual
may be changed at any time without notice. Varian reserves the right to make changes in
any products herein to improve reliability, function, or design. Varian does not assume
any liability arising out of the application or use of any product or circuit described
herein; neither does it convey any lice nse u n der it s pate nt rig ht s no r the rig hts of oth e rs.
Inclusion in this doc um e nt do es no t imp l y tha t any particular feature is sta nd ard on the
instrument.

ERCURYplus, MERCURY-Vx, MERCURY , Gemini, GEMINI 2000,

M

UNITY

INOVA, UNITYplus,
UNITY, VXR, XL, VNMR, VnmrS, VnmrX, VnmrI, VnmrV, VnmrSGI, MAGICAL II,
AutoLock, AutoShim, AutoPhase, limNET, ASM, and SMS are registered trademarks or
trademarks of V arian, Inc. Sun, Solaris, CDE, Suninstall, Ult ra, SPARC, SP ARCstation,
SunCD, and NFS are registered trademarks or trademarks of Sun Microsystems, Inc. and
SPARC International. Oxford is a registered trademark of Oxford Instruments LTD.
Ethernet is a registered trademark of Xerox Corpora tion. VxWORKS and VxWORKS
POWERED are registered trademarks of WindRiver Inc. Other product names in this
document are registered trademarks or trademarks of their respective holders.

Table of Contents

SAFETY PRECAUTIONS
Introduction
Chapter 1.

1.1 Line Broadening ......................................................................................................... 14

1.2 Spin-Lattice Relaxation Time ..................................................................................... 15

1.3 Solids Modules, Probes, and Accessories ................................................................... 15

Chapter 2.

2.1 CP/MAS Solids Modules ............................................................................................ 16

2.2 Rotor Characteristics and Composition ...................................................................... 20

2.3 Preparing Samples ...................................................................................................... 21

2.4 Spinning the Sample ................................................................................................... 22

2.5 Adjusting Homogeneity .............................................................................................. 29

2.6 Adjusting the Magic Angle ......................................................................................... 32

2.7 Calibrating the CP/MAS Probe ................................................................................... 35

2.8 Referencing a Solids Spectrum ............................... ...... .............................................. 37

2.9 XPOLAR1—Cross-Polarization ................................................................................. 38

2.10 Optimizing Parameters and Special Experiments ..................................................... 41

2.11 Useful Conversions ................................................................................................... 44

Chapter 3.

3.1 Wideline Solids Module .............................................................................................. 46

3.2 Wideline Experiments ............................................. ...... .............................................. 50

3.3 SSECHO Pulse Sequence ........................................................................................... 51

3.4 Data Acquisition ......................................................................................................... 51

3.5 Standard Wideline Samples ........................................................... ..... ...... .................. 53

3.6 Data Processing ........................................................................................................... 55

...................................................................................................... 12

Overview of Solid-State NMR ...................................................... 14

CP/MAS Solids Operation ............................................................ 16

Wideline Solids Module Operation ............... ............................... 46

............................ ........................................ ................ 8

Chapter 4.

4.1 Introduction to Multipulse Experiments ..................................................................... 56

4.2 CRAMPS/Multipulse Module Hardware ............................................ ........................ 57

4.3 Multipulse Experiments and User Library .................................................................. 60

4.4 Multipulse Tune-Up Procedure (FLIPFLOP) ............................................................. 60

4.5

4.6 How to Obtain Good CRAMPS Spectra ..................................................................... 65

4.7 Quadrature 1H CRAMPS ........................................................................................... 66

4.8 Fast MAS Assisted with a Multiple-Pulse Cycle (WaHuHaHS) ................................ 67

4.9 FLIPFLOP - Pulse Width and Phase Transient Calibration ........................................ 68

4.10 BR24 and CYLBR24 - Multiple Pulse Line Narrowing (24-pulse cycle) ................ 69

4.11 MREV8 and CYLMREV - Multiple Pulse Line Narrowing (8-pulse cycle) ........... 70

4.12 WaHuHa and WaHuHaHS - MP-Assisted High-Speed Spinning (4-pulse cycle) .... 71

CRAMPS/Multipulse Module Operation ...................................... 56

1

H CRAMPS Experiment (BR24 or MREV8) ........................................................... 64

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

4

Table of Contents

Chapter 5.

5.1 Pneumatics/Tachometer Box ...................................................................................... 72

5.2 Rotor Synchronization Operation ............................................................................... 72

5.3 Rotor Speed Controller Accessory Operation ............................................................ 76

5.4 Variable Temperature Operation with Solids ............................................................. . 78

Chapter 6.

6.1 XPOLAR—Cross-Polarization, UNITY .................................................................... 81

6.2 XPOLAR1—Cross-Polarization ................................................................................. 85

6.3 XPWXCAL—Observe-Pulse Calibration with Cross-Polarization ............................ 87

6.4 XNOESYSYNC—Rotor Sync Solids Sequence for Exchange .................................. 89

6.5 MASEXCH1—Phase-Sensitive Rotor Sync Sequence for Exchange ........................ 90

6.6 HETCORCP1—Solid-State HETCOR ....................................................................... 92

6.7 WISE1—Two-Dimensional Proton Wideline Separation .................................... ...... . 93

6.8 XPOLWFG1—Cross-Polarization with Programmed Decoupling ............................ 93

6.9 XPOLXMOD1—Waveform Modulated Cross-Polarization ...................................... 95

6.10 VACP—Variable Amplitude Cross-Polarization .................................... ..... ............. 97

6.11 XPOLEDIT1—Solids Spectral Editing ................................................................... . 98

6.12 3QMAS1—Triple-Quantum 2D for Quadrupole Nuclei .......................................... 99

6.13 PASS1—2D Sideband Separation for CP/MAS ..................................................... 101

6.14 CPCS—Cross-Polarization with Proton Chemical Shift Selection ........................ 102

6.15 CPCOSYPS—Cross-Polarization Phase-Sensitive COSY ..................................... 103

6.16 CPNOESYPS—Cross-Polarization Phase-Sensitive NOESY ........................... ..... 104

6.17 R2SELPULS1—Rotation Resonance with Selective Inversion ............................. 106

6.18 DIPSHFT1—Separated Local Field Spectroscopy ................................................. 108

6.19 SEDRA2—Simple Excitation of Dephasing Rotational-Echo Amplitudes ........... 109

6.20 REDOR1—Rotational Echo Double Resonance .................................................... 111

6.21 DOUBLECP1—Double Cross-Polarization ........................................................... 113

6.22 T1CP1—T

6.23 HAHNCP1—Spin 1/2 Echo Sequence with CP .............. ...... ................................. 116

6.24 SSECHO1—Solid-State Echo Sequence for Wideline Solids ................................ 117

6.25 WLEXCH1—Wideline Solids Exchange ............................................................... 119

6.26 HS90—90-Degree° Phase Shift Accuracy .............................................................. 121

6.27 MREVCS—Multiple Pulse Chemical-Shift Selective Spin Diffusion ................... 122

6.28 MQ_SOLIDS—Multiple-Quantum Solids ............................................................. 123

6.29 SPINDIFF—Spin Diffusion in Solids .................................................................... 124

6.30 FASTACQ—Multinuclear Fast Acquisition ........................................................... 124

6.31 NUTATE—Solids 2D Nutation .............................................................................. 125

Solid-State NMR Accessories ...................................................... 72

Solid-State NMR Experime n ts .............. ................ .. ................ ..... 80

Measurement with Cross-Polarization ................................................ 115

1

Index

.............. ................. ................ ................. .................. .................. ............ 128

5

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

List of Figures

Figure 1. Attenuator Control Graph for INOVA Systems ............................................................ 18

Figure 2. Attenuator Control Graph for Mercury Systems .......................................................... 18

Figure 3. Spinner Speed Control Window ................................................................................... 25

Figure 4. Spinner Speed Control Window ................................................................................... 27

Figure 5. Typical MAS Spectrum of Adamantane ....................................................................... 31

Figure 6. Coarse Adjustment of Sample Angle ........................................................................... 32

Figure 7. FID Display of KBr on Angle ...................................................................................... 34

Figure 8. FID Display of KBr 1/2 Turn Off Angle ...................................................................... 34

Figure 9. Typical Hexamethylbenzene (HMB) Spectrum ........................................................... 34

Figure 10. XPOLAR1 Pulse Sequence ........................................................................................ 38

Figure 11. Array of Contact Times .............................................................................................. 41

Figure 12. TOSS Experiment on Alanine (Spectrum and Sequence) .......................................... 42

Figure 13. Protonated Carbon Suppression of Alanine (Spectrum and Sequence) ..................... 43

Figure 14. Rotating-Frame Spin-Lattice Relaxation Measurements Sequence ........................... 43

Figure 15. Pulse Sequence for Measuring

Figure 16. Solids Cabinet Layout, Open Front View ................................................................... 48

Figure 17. Real Channel FID Pattern ........................................................................................... 62

Figure 18. FLIPFLIP FID at Exact 90

Figure 19. FLIPFLOP “Tram Tracks” ......................................................................................... 63

Figure 20. FLIPFLOP Desired FID ............................................................................................. 63

Figure 21. Adipic Acid Spectrum ................................................................................................ 65

Figure 22. Pulse Sequence for flipflop.c ...................................................................................... 68

Figure 23. BR24 Pulse Sequence ................................................................................................. 69

Figure 24. MREV8 Pulse Sequence ............................................................................................ 70

Figure 25. WaHuHa Pulse Sequence ........................................................................................... 71

Figure 26. Pneumatics/Tachometer Box for CP/MAS Probes .................................................... 73

Figure 27. Different Modes of the Rotor Synchronization Accessory ........................................ 73

Figure 28. Base of a Varian High-Speed Spinning Rotor ............................................................ 74

Figure 29. Doty Double Bearing Rotor ....................................................................................... 74

Figure 30. TOSS Pulse Sequence ................................................................................................ 82

Figure 31. Protonated Carbon Suppression Sequence ................................................................. 83

Figure 32. Rotating-Frame Spin-Lattice Relaxation Measurements Sequence ........................... 83

Figure 33. Pulse Sequence for Measuring

Figure 34. XPOLAR1 Pulse Sequence ........................................................................................ 85

Figure 35. XPWXCAL Pulse Sequence ...................................................................................... 88

Figure 36. XNOESYSYNC Pulse Sequence ............................................................................... 89

Figure 37. MASEXCH1 Pulse Sequence .................................................................................... 91

Figure 38. XPOLXMOD1 Pulse Sequence ................................................................................. 95

Figure 39. VACP Pulse Sequence ................................................................................................ 97

Figure 40. XPOLDIT1 Pulse Sequence ....................................................................................... 98

l

H T1 .......................................................................... 44

° Pulse .............................................................................. 62

l

H T1 .......................................................................... 84

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

6

List of Figures

Figure 41. 3QMAS1 Pulse Sequence .......................................................................................... 99

Figure 42. PASS1 Pulse Sequence ............................................................................................. 101

Figure 43. CPCS Pulse Sequence .............................................................................................. 102

Figure 44. CPCOSYPS Pulse Sequence .................................................................................... 104

Figure 45. CPNOESYPS Pulse Sequence ................................................................................. 105

Figure 46. R2SELPULS1 Pulse Sequence ................................................................................ 107

Figure 47. DIPSHFT1 Pulse Sequence ...................................................................................... 108

Figure 48. SEDRA2 Pulse Sequence ......................................................................................... 110

Figure 49. REDOR1 Pulse Sequence ........................................................................................ 112

Figure 50. DOUBLECP1 Pulse Sequence ................................................................................. 114

Figure 51. T1CP1 Pulse Sequence ............................................................................................. 115

Figure 52. HAHNCP1 Pulse Sequence ...................................................................................... 116

Figure 53. SSECHO1 Pulse Sequence ....................................................................................... 118

Figure 54. WLEXCH1 Pulse Sequence ..................................................................................... 120

Figure 55. HS90 Pulse Sequence ............................................................................................... 121

Figure 56. MREVCS Pulse Sequence ........................................................................................ 122

Figure 57. MQ_SOLIDS Pulse Sequence .................................................................................. 123

Figure 58. SPINDIFF Pulse Sequence ....................................................................................... 124

Figure 59. FAS TACQ Pulse Sequence ....................................................................................... 125

Figure 60. NUTATE Pulse Sequence ......................................................................................... 126

List of Tables

Table 1. Background Nuclei of Rotor Material ............................................................................. 19

Table 2. Typical Spin Rates with Associated Bearing and Drive Values ....................................... 21

Table 3. Reference Materials and

Table 4. Bessel Filter Outputs ........................................................................................................ 35

Table 5. Wideline Experiment Commands and Parameters ........................................................... 38

Table 6. Rotor Synchronization Controls ...................................................................................... 53

Table 7. Rotor Controller Gain Setting and Typical Ranges ......................................................... 55

Table 8. Multiacquisition Quadrature Corrections for MREV8 .................................................... 99

Table 9. Multiacquisition Quadrature Corrections for BR24 ...................................................... 100

Table 10. Multiacquisition Quadrature Corrections for CORY24 ............................................... 100

13

C Chemical Shifts ................................................................. 32

7

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

SAFETY PRECAUTIONS

The following warning and caution notices illustrate the style used in Varian manuals
for safety precaution notices and explain when each type is used:

W ARNING:

CAUTION:

Warnings

could result in injury or death to humans or animals, or significant
property damage.

Cautions

serious damage to equipment or loss of data.

Warning Notices

Observe the following precautions during installation, operation, maintenance, and
repair of the instrument. Failure to comply with these warnings , or with specific
warnings elsewhere in Varian manuals, violates safety standards of design,
manufacture, and intended use of the instrument. Varian assumes no liability for
customer failure to comply with these precautions.

W ARNING:

Persons with implanted or attached medical devices such as
pacemakers and prosthetic parts must remain outside the 5-gauss
perimeter of the magnet.

The superconducting magnet system generates stron g mag netic f ields that can
affect operation of some cardiac pacemakers or harm implanted or attached
devices such as prosthetic parts and metal blood vessel clips and clamps.

Pacemaker wearers should consult the user manu al provided by the pac emaker
manufacturer or contact the pacemaker manufacturer to determine the ef fect on
a specific pacemaker. Pacemaker wearers should also always notify their
physician and discuss the health risks of being in proximity to magnetic fields.
Wearers of metal prosthetics and implants should contact their physician to
determine if a danger exists.

Refer to the manuals supplied with the magnet for the size of a typical 5-gauss
stray field. This gauss level should be checked after the magnet is installed.

are used when failure to observe instructions or precautions

are used when failure to observe instructions could result in

W ARNING:

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

Keep metal objects outside the 10-gauss perimeter of the magnet.

The strong magnetic field surrounding the magnet attracts objects containing
steel, iron, or other ferromagnetic materials, which includes most ordinary
tools, electronic equipment, compressed gas cylinders, steel chairs, and steel
carts. Unless restrained, such objects can suddenly fly towards the magnet,
causing possible personal injury and extensi ve damag e to the probe, dewar , and
superconducting solenoid. The greater the mass of the object, the more the
magnet attracts the object.

Only nonferromagnetic materials—plastics, aluminum, wood, nonmagnetic
stainless steel, etc.—should be used in the area around the magnet. If an object
is stuck to the magnet surface and cannot easily be removed by hand, contact
Varian service for assistance.

8

SAFETY PRECAUTIONS

Warnin g Notic es (

Refer to the manuals supplied with the magnet for the size of a typical 10-gauss
stray field. This gauss level should be checked after the magnet is installed.

W ARNING:

W ARNING:

W ARNING:

Only qualified maintenance personnel shall remove equipment covers
or make internal adjustments.

Dangerous high voltages that can kill or injure exist inside the instrument.
Before working inside a cab inet, turn off the main system po wer switch loca ted
on the back of the console.

Do not substitute parts or modify the instrument.

Any unauthorized modification could injure personnel or damage equipment
and potentially terminate the warranty agreements and/or service contract.
Written authorization approved by a Varian, Inc. product manager is required
to implement any changes to the hardware of a Varian NMR spectrometer.
Maintain safety features by referring system service to a Varian service office.

Do not operate in the presence of flammable gases or fumes.

Operation with flammable gases or fumes present creates the risk of injury or
death from toxic fumes, explosion, or fire.

continued

)

W ARNING:

W ARNING:

W ARNING:

W ARNING:

Leave area immediately in the event of a magnet quench.

If the magnet dewar should quench (sudden app earance of gasses fro m the top
of the dewar) , leave the area immediately . Su dden release of helium or nitr ogen
gases can rapidly displace oxygen in an enclosed space creating a possibility of
asphyxiation. Do not return until the oxygen level returns to normal.

Avoid helium or nitrogen contact with any part of the body.

In contact with the body, helium and nitrogen can cause an injury similar to a
burn. Never place your head over the helium and nitrogen exit tubes on top of
the magnet. If helium or nitrogen contacts the body, seek immediate medical
attention, especially if the skin is blistered or the eyes are affected.

Do not look down the upper barrel.

Unless the probe is removed from the magnet, never look down the upper
barrel. You could be injured by the sample tube as it ejects pneumatically from
the probe.

Do not exceed the boiling or freezing point of a sample during variable
temperature experiments.

A sample tube subjected to a change in temperature can build up excessive
pressure, which can break the sample tube glass and cause injury by flying glass
and toxic materials. To avoid this hazard, establish the freezing and boiling
point of a sample before doing a variable temperature experiment.

9

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

SAFETY PRECAUTIONS

Warnin g Notic es (

W ARNING:

W ARNING:

W ARNING:

Support the magnet and prevent it from tipping over.

The magnet dewar has a high center of gravity and could tip over in an
earthquake or after being struck by a large object, injuring personnel and
causing sudden, dangerous release of nitrogen and helium gasses from the
dewar . Therefore, the magnet must be supported by at least on e of two methods:
with ropes suspended from the ceiling or with the antivibration legs bolted to
the floor. Refer to the Installation Planning Manual for details.

Do not remove the relief valves on the vent tubes.

The relief valves prevent air from entering the nitrogen and helium vent tubes.
Air that enters the magnet contains moisture that can freeze, caus ing block age
of the vent tubes and possibly extensive damage to the magnet. It could also
cause a sudden dangerous release of nitrogen and helium gases from the de war.
Except when transferring nitrogen or h elium, be certain that the relief valv es are
secured on the vent tubes.

On magnets with removable quench tubes, keep the tubes in place
except during helium servicing.

On Varian 200- and 300-MHz 54-mm magnets only, the dewar includes
removable helium vent tubes. If the magnet dewar should quench (sudden
appearance of gases from the top of the dewar) and the vent tubes are not in
place, the helium gas would be partially v ented side ways, po ssibly injuring the
skin and eyes of personnel beside the magnet. During helium servicing, when
the tubes must be removed, follow carefully the instructions and safety
precautions given in the magnet manual.

continued

)

Caution Notices

Observe the following precautions during installation, operation, maintenance, and
repair of the instrument. Failure to comply with these ca utions, or with specific
cautions elsewhere in Varian manuals, violates safety standards of design,
manufacture, and intended use of the instrument. Varian assumes no liability for
customer failure to comply with these precautions.

CAUTION:

Keep magnetic media, ATM and credit cards, and watches outside the
5-gauss perimeter of the magnet.

The strong magnetic field surrounding a superconducting magnet can erase
magnetic media such as floppy disks and tapes. The field can also damage the
strip of magnetic media found on credit cards, automatic teller machine (ATM)
cards, and similar plastic cards. Many wrist and pocket watches are also
susceptible to damage from intense magnetism.

Refer to the manuals supplied with the magnet for the size of a typical 5-gauss
stray field. This gauss level should be checked after the magnet is installed.

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

10

SAFETY PRECAUTIONS

Caution Notices (

CAUTION:

CAUTION:

CAUTION:

Check helium and nitrogen gas flowmeters daily.

Record the readings to establish the operating level. The readings will vary
somewhat because of changes in barometric pressure from weather fronts. If
the readings for either gas should change abruptly, contact qualified
maintenance personnel. Failure to correct the cause of abnormal readings could
result in extensive equipment damage.

Never operate solids high-power amplifiers with liquids probes.

On systems with solids high-power amplifiers, never operate the amplifiers
with a liquids probe. The high power available from these amplifiers will
destroy liquids probes. Use the appropriate high-power probe with the high­power amplifier.

Take electrostatic discharge (ESD) precautions to avoid damage to
sensitive electronic components.

Wear grounded antistatic wristband or equivalent before touching any parts
inside the doors and covers of the spectrometer system. Also, take ESD
precautions when working near the exposed cable conn ectors on the back of the
console.

continued

)

Radio-Frequency Emis sion Regulations

The covers on the instrument form a barrier to r adi o-f r eque nc y (rf) energy. Removing
any of the covers or modifying the instrument may lead to increased susceptibility to
rf interference within the instrument and may increase the rf ener gy tr ansmitted by the
instrument in violation of regulations covering rf emissions. It is the operator’s
responsibility to maintain the instrument in a condition that does not violate rf emission
requirements.

11

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

Introduction

This manual is designed to help you perform solid-state NMR experiments using a Varian
solid-state NMR module on a Varian NMR spectrometer system running VNMR version

6.1C software. The manual contains the following chapters:

• Chapter 1, “Overview of Solid-State NMR,” provides an short overview of solid-state
NMR, including the types of solids modules, probes, and accessories available.

• Chapter 2, “CP/MAS Solids Operation,” cover s usin g th e CP/M AS so lids modu le and
related pulse sequences.

• Ch apter 3, “Wideline Solids Module Operation,” covers using the wideline solids
module.

• Chapter 4, “CRAMPS/Multipulse Module Operation,” covers using the CPAMPS/
multipulse module and related pulse sequences.

• Chapter 5, “Solid-State NMR Accessories,” covers using the rotor synchronization,
rotor speed controller accessory, and solids variable temperature accessories.

• Ch apter 6, “Solid-State NMR Experiments,” is a guide to pulse sequences useful for
performin g solid-state NMR experiments.

Notational Conventions

The following notational conventions are used throughout all VNMR manuals:

• Typewriter-like characters identify VNMR and UNIX commands, parameters,
directories, and file names in the text of the manual. For example:

The shutdown command is in the /etc directory.

• The same type of characters show text displayed on the screen, including the text
echoed on the screen as you enter commands during a procedure. For example:

Self test completed successfully.

• Text shown between angled brack ets in a syntax entry is optional. For example, if the
syntax is seqgen s2pul<.c>, entering the “.c” suffix is optional, and typing
seqgen s2pul.c or seqgen s2pul is functionally the same.

• Lines of text containing command syntax, examples of statements, source code, and
similar material are often too long to fit the width of the page. To show that a line of
text had to be broken to fit into the manual, the line is cut at a convenient point (such
as at a comma near the right edge of the column) , a backslash (\) is inse rted at the cut,
and the line is continued as the next line of text. This notation will be familiar to C
programmers. Note that the backslash is not part of the line and, except for C source
code, should not be typed when entering the line.

• Because pressing the Return key is required at the end of almost every command or
line of text you type on the keyboard, use of the Return key will be mentioned only in
cases where it is not used. This convention avoids repeating the instruction “press the

Return key” throughout most of this manual.

• Text with a change bar (like this paragraph) identifies material new to VNMR 6.1C that
was not in the previous version of VNMR. Refer to the document Release Notes for a
description of new features to the software.

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

12

Introduction

Other Manuals

This manual should be your basic source for information about using the spectrometer
hardware and software on a day-to-day basis for solid-state NMR. Other VNMR manuals
you should have include:

All of these manuals are shipped with the VNMR software. These manuals, other Varian
hardware and installation manuals, and most Varian accessory manuals are also provided
online so that you can view the pages on your workstation and print copies.

Types of Varian NMR Spectrometer Systems

• Getting Started

• Walkup NMR Using GLIDE

• User Guide: Liquids NMR

• VNMR Command and Parameter Reference

• VNMR User Programming

• VNMR and Solaris Software Installation

In parts of this manual, the type of spectrometer system (

ERCURY, GEMINI 2000, UNITYplus, UNITY, or VXR-S) must be considered in order to

M

UNITY

INOV A, MERCURY-VX,

use the software properly.

UNITY

INOV A and MERCURY-VX are the current systems sold by Varian.

•

UNITY

• UNITYplus, UNITY, and VXR-S are spectrometer lines that preceded the

• M

ERCURY and GEMINI 2000 are spectrometer lines that preceded the MERCURY-VX.

INOVA.

Help Us to Meet Your Needs!

We want to provide the equipment, publications, and help that you want and need. To do
this, your feedback is most important. If you have ideas for improvements or discover a
problem in the software or manuals, we encourage you to contact us. You can reach us at
the nearest Varian Applications Laboratory or at the following address:

Palo Alto Applications Laboratory
Varian, Inc., NMR Systems
3120 Hansen Way, MS D-298
Palo Alto, California 94304 USA

13

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

Chapter 1.

Overview of Solid-State NMR

Sections in this chapter:

• 1.1 “Line B roadening,” this page

• 1.2 “Spin-Latti ce Relaxation Time,” page 15

• 1.3 “Solids Modules, Probes, and Accessories,” page 15

Before techniques were developed to obtain high-resolution NMR spectra of compounds in
the solid state, the spectra of these samples were generally characterized by broad,
featureless envelopes caused by additional nuclear interactions present in solid state. In
liquid state, these interactions average to zero due to rapid molecular tumbling.

1.1 Line Broadening

One cause of line broadening is heteronuclear and homonuclear dipolar coupling. Th is
coupling arises from the interaction of the nuclear magnetic dipole under observation with
those of the surrounding nuclei, and is directly proportional to the magnetogyric ratios of
the nuclei and inversely proportional to the distance between them. In strongly coupled
organic solids, the heteronuclear dipolar coupling between a
proton can be 40 kHz. In or der to remove the heteronucle ar dipolar co upling, a strong rf
field equal to or greater than the interaction energy mu st be applied at the proton r esonance
frequency.

13

C nucleus and a bonded

A second cause of line broadening in polycrystalline compounds is chemical shift
anisotropy (CSA) . This is the result of nuclei with different orientations in the applied
magnetic field resonating at different Larmor frequencies. The observed spread of the
chemical shifts is called the chemical shift anisot ropy and can be as large as a fe w hundred
ppm. This interaction can be removed by rapidly rotating the sample about an axis oriented
at an angle of 54 degrees 44 minutes (54.73
or MAS to the applied magnetic field. The spinning speed of the sample must be greater
than the CSA in order to reduce the resonance to a single, narrow (approximately 1 ppm)
line at the isotropic frequency. If the spinning speed is less than the CSA, a pattern of
sidebands occurs about the isotro pic peak at integral v alues of the spinning frequenc y. The
CSA scales linearly with B

A third source of line broadening in solids occurs when observing nuclei that possess an
electric quadrupole. The quadrupolar int eraction can be as large as several MHz. For
nonintegral spin quadrupolar nuclei, the central transition is much narrower (about 10 kHz)
and therefore can be narrowed to a single, narrow line by magic angle spinning. The
residual (second order) linewidth of the central transition is inversely proportional to the
applied magnetic field.

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

.

0

°, the “magic angle” in magic angle spinning,

14

Chapter 1. Overview of Solid-State NMR

1.2 Spin-Lattice Relaxation Time

An additional characteristic of some nuclei in the solid state, for example 13C, is a long
spin-lattice relaxation time (T

). To overcome this problem, the abundant nuclei (usually

1

protons) in the system are used. These are polarized with a spin locking pulse (CP). The
polarization is then transferred to the rare spins by applying an rf field at the Larmor
frequency of the rare spins that is of such a magnitude as to make the energy levels of the
abundant and rare spins the same in the rotating frame (Hartmann-Hahn match condition).
Following a transfer of ener gy fr om the polarized ab undant spins to the rare spins, the rare
spin field is turned off and the resulting signal observed under conditions of high-power
proton decoupling. The recycle time is then set accor ding to the proton T
much shorter than the rare spin T

.

1

The polarization transfer can give an increase in sensitivity. The rare spin response is
enhanced by a factor of up to the ratio of the magnetogyric ratios of the two spin systems.

13

For the

C-{1H} system, this is a factor of 4. However, as the enhancement is distance
related, caution should be exercised in using the cross-polarization experiment for
quantitative analysis.

1.3 Solids Modules, Probes, and Accessories

, which is usually

1

Varian supplies a complete line of solid-state NMR modules, probes, and accessories.
Solids modules include CP/MAS, wideline, CRAMPS/m ult ipulse, and complete solids.

CP/MAS, wideline, and CRAMPS/Multipulse hardware and operation are covered in
Chapters 2, 3, and 4, respectively, of this manual.

The Varian complete solids module is capable of performing all experiments possible with
the Varian CP/MAS, wideline, and CRAMPS/multipulse modules. The major components
of complete solids module are the following:

UNITY

INOVA o r UN ITYplus System Wideband ADC with Sum to Memory

Solids cabinet
High-band & low-band 1-kW amplifier
Pneumatics/tachometer box

MERCURYplus and MERCURY-Vx
systems

100 Watt High-band and 300 Low-band
amplifiers for CP/MAS experiments
Pneumatics/tachometer box

UNITY or VXR-S System Wideband ADC

Solids cabinet
High-band & low-band 1-kW amplifier
Pneumatics/tachometer box
Wideband receiver
Sync module
Two fine att enuators

For operation of the complete solids module, refer to the operations sections in the chapters
2 to 4 for the CP/MAS, wideline, and CRAMPS/multipulse mo dules.

15

A wide variety of solids probes and probe accessories are available, including wideline,
multipulse, and magic-angle probes.

Optional solids accessories include rotor synchronization, rotor speed controller, and the
solids variable temperature accessory. Chapter 5 covers using these accessories.

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

Chapter 2.

Sections in this chapter:

• 2.1 “CP/MAS Solids Modules,” this page.

• 2.2 “Rotor Characteristics and Composition,” page 20.

• 2.3 “Preparing Samples,” page 21

• 2.4 “Spinning the Sample,” page 22.

• 2.5 “Adjusting Homogeneity,” page 29.

• 2.6 “Adjusting the Magic Angle,” page 32.

• 2.7 “Calibrating the CP/MAS Probe,” page 35.

• 2.8 “Referencing a Solids Spectrum,” page 37

• 2.9 “XPOLAR1—Cross-Polarization,” page 38

• 2.10 “Optimizing Parameters and Special Experiments,” page 41.

• 2.11 “Useful Conversions,” page 44.

CP/MAS Solids Operati on

2.1 CP/MAS Solids Modules

CP/MAS hardware differs between systems. This section provides an overview of the
hardware (excluding probes) for:

UNITY

INOV A, UNITYplus, and UNITY systems with 100/300 Watt CP/MAS accessory

•

UNITY

INOV A, UNITYplus, and UNITY systems with a full solids bay co ntaining one or

•
more 1 kW amplifiers

• MERCURYplus and MERCURY-Vx systems with the 100/300 CP/MAS option

CP/MAS Hardware for 100/300 Watt Systems

The CP/MAS option is available for most narrow bore UNITY and all
UNITYplus, MERCURYplus and MERCURY-Vx systems. A class A/B AMT 3900A-15
linear amplifier, with a maximum output of 100 W for up to 2 50 ms, replaces the standard

1H/19

F liquids linear amplifier for all systems.
systems use the standard lowband amplifier which has an output of 300 W. The
MERCURYplus and MERCURY-Vx system lowband amplifier is replaced by the 300 W
lowband amplifier used in the

UNITY

The

INOV A, UNITYplus, and UNITY system CP/MAS accessory amplifier chassis is
distinguished from standard amplifier chassis by the presence of three amplifier bricks as
compared to two amplifier bricks in the standard chassis. The MERCURYplus and
MERCURY-Vx system CP/MAS amplifier chassis is housed in an accessories console
attached to the standard console.

UNITY

INOVA system.

UNITY

UNITY

INOVA, UNITYplus, and UNITY

INOVA,

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

16

Chapter 2. CP/MAS Solids Operation

Full-Solids 1H/19F 1 kW Amplifiers

UNITY

INOV A, UNITYplus, and UNITY wide bore systems can be equipped with the full bay
solids option that includes a 1 kW
amplifier, tunable to either
produces 1 kW at 400 MHz and below. Power output at 500 to 900 MHz is lower and
specifications are available for individual amplifiers.

Cavity tuned amplifiers used in older systems are distinguished from the current amplifiers
by the external control box used to tune the cavity . These older amplif iers are often referred
to as CPI amplifiers in recognition of the manufacturer of the tube.

Current and newer systems incorporate the CMA amplifier manufactured in Fort Collins,
Colorado, USA by Varian Inc. These amplifiers offer the option of either class AB or class
C operation. CMA amplifiers are tuned manually using calibrated tuning knobs. The
amplifier is enabled or disabled using the switches on the fro nt pan el of the fu ll solids bay.

• Enable hi gh power amplifier operation
Place the

illuminate) and enable high power with the silver button (a green LED will illuminate).

• Disable high power amplifier operation
Place the

button. The 50 W amplifier remains enabled.

HI BAND amplifier switch in the HI POWER position (an orange LED will

HI BAND amplifier switch in the LO POWER position and press the red

1H/19

1

H or 19F , dri v en by the stan dard 50 W high band amplifier , and

F amplifier. The amplifier is a class AB tube

CPI and CMA amplifiers operate in both pulsed and continuous (CW) modes. The
parameter ampmode is used to select the operation mode for CPI amplifiers. When the
parameter ampmode is not present the amplifier is set in the default CW mode (

‘c’

or

‘d’

=

CLASS C, CLASS AB (CW), or GATE ACTIVE (pulsed), are selected using the three

position switch on the front panel of the amplifier. Set the switch to
CP/MAS experiments,

) which is correct for CP/MAS experiments. CMA amplifier modes;

CLASS AB mode for

GATE ACTIVE mode for

1

H or 19F observe, or CLASS C for special

ampmode

multipulse exper iments. The ampmode parameter must be either set to the correct value or

1H/19

in the default mode as it determines the operation of the 50 W

F amplifier that drives

the CMA amplifier.

Full-Solids Lowband 1 kW Amplifiers

The high power lowband amplifier in the full solids bay is a class A linear amplifier and is
either an AMT 3201 (older systems) or AMT 3200 series amplifier. These amplifiers
produce 1 kW at full power o ver a range of 6 to 220 MHz (up to

13

500 MHz or

C for systems with 1H at 900 MHz).

The 3201 amplifier on older systems does not hav e a po wer meter on the front panel. Input
to the older amplifier is from the standard 300 W lowband amplifier in the console. The
high power amplifier is enabled or disabled using the switches on the front panel of the full
solids bay.

• Enable hi gh power amplifier operation
Place the

LO BAND amplifier switch in the HI POWER position (an orange LED will

illuminate) and enable high power with the silver button.

• Disab le the high power amplifier and return to the standard amplifier

LO BAND amplifier switch in the LO POWER position and press the red button.

Place
The 300 W amplifier remains enabled.

The 3200 amplifier on newer systems has a power meter on the front panel. Input drive is
provided by the milliwatt transmitter board in the console. The high power amplifier is
enabled or disable using the switches on the front panel of the full solids bay.

31

P for systems with 1H at

17

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

2.1 CP/MAS Solids Modules

6

2

8

4

0

• Enable hi gh power amplifier operation
Place the LO BAND amplifier switch in the HI POWER position (an orange LED will

illuminate) and enable high power with the silver button.

• Disab le the high power amplifier operation

LO BAND amplifier switch in the LO POWER position and press the red button.

Place
If a 300 W lowband amplifier is present in the console it will now be enabled.

Low-band amplifiers operate in either pulsed or CW mode. The operation mode is
controlled by the ampmode parameter. When the parameter ampmode is not present the
amplifier is set in the default (CW) mode (ampmode = ‘c’ or ‘d’) which is correct for
CP/MAS experiments.

Fine Attenuators

UNITY

INOVA and UNITYplus Systems

The standard

UNITY

INOV A
and UNITYplus system
transmitter board
provides fine power
control over a range of 0
to 60 dB in 4095 steps.
Output in voltage or f ield
strength is linear and
quadratic in power. The
attenuator control in dB
is shown in Figure 1. A
rough rule is; for a 2 fold
change in fine power
there is a 6 db change in
the coarse power (tpwr or dpwr). Power is controlled using the parameters: tpwrf,
dpwrf, dpwrf2, and dpwrf3. Aliases of these parameters ending in m rather than f are
used in some pulse sequences, including XPOLAR1. The parameters crossp and
dipolr in XPOLAR1 are two different values that set dpwrf during the cross
polarization and decoupling periods respectively.

65
60
55
50
45

dB

40

3

35
30

0 1000 2000 3000 4000

4

4

5

Attenuator Value

Figure 1. Attenuator Control Graph for INOVA Systems

6

MERCURYplus and MERCURY-Vx Systems

The transmitter board
provides fine power
control over a range of
0 up to 40 db in 255
amplitude steps using
the parameters tpwrf
and dpwrf. Output in
voltage or field strength
is linear and quadratic in
power. The attenuator
control in dB is shown in

Figure 2.

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

50
45
40

dB

35
30
25

24

20

0 50 100 150 200 250 300

36

30

42

Attenuator Value

48

Figure 2. Attenuator Control Graph for Mercury Systems

18

Chapter 2. CP/MAS Solids Operation

UNITY Systems

Fine attenuator control is provided over a 6 db range in steps from 0 of 4095 on on e or both
transmitter boards. It is necessary to use both the fine and course attenuators on UNITY
systems to set the power levels for CP/MAS experiments. UNITY systems use the same
XPOLAR1 aliases described above. In add itio n a new coarse power setting, cppwr (alias
for dpwr) used during cross polarization, is crated by setting dblvl2=’y’. The
parameter dpwr then applies only to the decoupling power. UNITY systems with a fine
attenuator only on the highband channel must first set the observe power using the course
attenuator and then high band channel using both t he course and fine attenu ators. CP/MAS
is very difficult if the fine attenuators are absent on both channels.

The XPOLAR sequence (described in older versions of this manual) can be used with
UNITY systems.

Pneumatics and Tachometer Box and Rotor Speed Control

A pneumatics/tachometer box is used for controlling air flo w and spinning speeds of MAS
rotors for all systems. A manu al box allows adjustment of bearing and drive pressure with
knobs and is independent of the console. Alternatively a rotor s peed co ntro ller is available

UNITY

for
obtained by modulation of the drive flow and is under computer control. Th e Rotor Sp eed
Controller tachometer box is distinguished from the manual tachometer box by a 9 pin
connector on the lower righ t. The connector is used to connect the optional cable from the
tachometer box to the back of the acquisition computer on
board in the magnet leg on MERCURY systems. Rotor speed control software is located in
the MSR board of INOVA and the Spinner board of MERCURY s ystems. A
system equipped with both the Rotor Synchronization and Rotor Speed Control options and
appropriate cables for the acquisition computer can trigger pulses on the tachometer signal
using the pulse sequence commands xgate, rorotsync, and rotorperiod.

The operation of the Pneumatics and T achometer Box is described in section 2.4 “Spinning

the Sample,” page 22.

INOVA and all MERCURY systems with the solid option. Rotor speed control is

UNITY

INOVA or the to Spinner

UNITY

INOVA

19

An older standalone PC may be present to provide rotor speed control for UNITYplus and
UNITY. Instructions for this co ntroller are provided in older manuals.

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

2.2 Rotor Characteristics and Composition

2.2 Rotor Characteristics and Composition

Varian high-speed rotors (with and without vent holes) are composed of zirconia or of
silicon nitride (Si
rotor body and is held with two O-rings. Always check the maximum spin rate specification
for Varian rotors and end caps as listed Table 1.

Table 1. Characteristics of Varian Rotors and End Caps

) with pMMA, Kel-f, or Torlon end caps. The cap twist-fits into the

3N4

Item Material Color

Rotor,
7 mm

Rotor,
7 mm

Rotor,
5 mm

Rotor,
5 mm

Cap,
7 mm

Cap,
7 mm

Cap,
5 mm

Cap,
5 mm

Cap,
7 mm

Cap,
5 mm

Cap,
7 mm

Cap,
5 mm

Cap,
5 mm

Zirconia white or

off-white

Silicon
nitride

Silicon
nitride

Silicon
nitride

Torlon green –125° to +125° 9500 9000 00-991646-01

Torlon,
vented

Torlon green –125° to +125° 15000 9000 00-992519-00

Torlon,
vented

pMMA colorless-

Kel-F,
vented

Kel-F colorless-

Kel-F colorless-

Kel-F colorless-

gray –125° to +125° 9500 9000 00-990874-00

gray –125° to +125° 15000 13000 00-992521-00

gray
(CRAMPS)

green –125° to +125° 5000 — 00-991647-00

green — 5000 — 00-992524-00

clear
colorless-

opaque

opaque

opaque

opaque

Recommended
Temperature
Range (C)

— 7200 — 00-991036-00

–125° to +125° 15000 13000 00-993263-00

–125° to
ambient

–125° to
+ 80°

–125° to
+ 80°

–125° to
+ 80°

–125° to
+ 80°

Max Spin Rate
Ambient
(Hz)

9500 9000 00-991038-00

5000 5000 01-902171-00

7000 7000 00-992558-00

7000 7000 00-993228-00

7000 7000 00-993262-00

Max Spin
Rate VT
(Hz)

Varian Part No.

Current Si

rotors are of two-piece construction. If the roto r plu g br eaks loos e fro m the

3N4

rotor body, reinsert the plug and secure it with cyanoacrylate.
T achometer sensing on high-speed rotors is on the rotor bot tom. Zirconia rotors are marked

with a permanent black marking pen or black enamel paint so that 50% of the bottom of
surface area is shaded black; silicon nitride (Si

) rotors are marked with white enamel

3N4

paint in the same fashion. Centrifugal force and rotor crashes cause the black and white
markings to flake off around the edges resulting in inaccurate tachometer readings. Reapply
the black or white half circle. Make the diameter marking straight.

Below -100
exists. Kel-F end caps (colorless-opaque) have a VT upper limit of about +70

°C, a potential for slipping due to differential contraction with the ceramic rotor

°C and should

not be spun faster than 65 00 Hz at an y tem perature. Use pMMA ( colorless -clear) end caps
only at room temperature and below. Visually distinguishing between Kel-F and pMMA
end caps can be difficult, so you may want to mark them appropriately.

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

20

Chapter 2. CP/MAS Solids Operation

Rotor and end cap compositions are given in Table 2.

Table 2. Background Nuclei of Rotor Material

Material Background

Kel-F end cap C (not cross-polarizable from H), F (cross-polarizable)
Vespel, Torlon, pMMA end cap C (cross-polarizable), H
zirconia rotor* Zr, O, traces of Mg, Y, Al

rotor** Si, N, some Al

Si

3N4

*Not recommended for CP/MAS experiments.
**Use Si

rotors only for high power CP/MAS applications.

3N4

2.3 Preparing Samples

Solid samples are normally packed into hollow rotors and sealed with fluted caps. The
method of filling the rotors depends somewhat on the form and nature of the sample. The
most critical factor in spinning reliability is the dynamic balance of the filled rotor. Some
specific recommendations on filling the rotors and achieving a reasonable balance for
different kinds of samples are given below.

Homogeneous Machinable Solids

Although some hard machinable polymers can be made directly into solid rotors, it is much
easier to make a plug for the standard hollo w rotor . The signal-to-noise difference is not that
significant. The fit must be tight enough to prevent the plug from rattling around or slipping
out during spinning. The sample material must be homogeneous and free of voids for the
spinning rotor to remain balanced.

One way to remove a sample plug is to drill and tap a center hole about halfway through
the plug for a 2-56 screw. This is best done on a lathe to facilitate centering and ensure
balance. A small screw is then used to extract the plug.

Machine samples of solid materials to 0.440
diameter of 0.1960

± 0.0005 in. (4.979 mm) for Varian 7-mm rotors or 0.137 in. (3.48 mm)

± 0.005 in. (11.176 mm) in length with a

for Varian 5-mm rotors and placed inside a rotor.

Granular and Powdered Materials

The best method for filling the rotors with granular or powder materials is to pour the
material into the rotor and leave just enough room for the cap. Granular and powdered
materials work best as uniform particles of 100 mesh or finer. If the material can be ground,
do so before attempting to pack the rotor (a mortar and pestle is usually sufficient). Fluffy
or flaky materials can be packed with a rod machin ed to a slightly smaller diameter than the
internal diameter (ID) of the rotor. Hand pressure is sufficient. Hard packing with a press
or hammer is not necessary and can damage the rotors. The ca p works best if it is in contact
with the top of the sample material and fits snug and flush with the top of the rotor.

21

Miscellaneous Materials

Sample material types and forms exist that are not machinable solids, granular, or
powdered. Some of these materials can be prepared in rotors so that dynamic balance is

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

2.4 Spinning the Sample

preserved. Chances are good that the sample will spin adequately if the material can be
made to fill the rotor homogeneously.

Thick sheet or film materials are best handled by cutting or punching many disks, each
having the inside diameter of the rotor, and stacking them in the rotor until full.

Coarse and irregular granular materials as well as pellets, beads, flak es, bits, or pieces often
cannot be packed homogeneousl y en oug h to p ro vide the balance n ecessa ry for high speed
spinning. Sometimes such materials can be made to spin smoothly by filling the voids with
a fine powder that does not give NMR signals, such as KBr, talc, or sulfur flowers and
spinning at a lower speed.

Liquid Samples

CAUTION:

Use an end cap that has a concentric hole drilled through it (a #73 drill is recommended)
for liquid samples. Be sure the end cap will not dissolve (organic solvents can dissolve
pMMA end caps). Liquid samples can be spun at 200 to 300 Hz, but the liquid may spin
out of the rotor and be lost. This fact must be considered when dealin g with toxic or noxious
samples.

Organic solvents can dissolve pMMA end caps.

Semi-Solid Samples

Semi solid samples such as phospholipid suspens ions can spin faster then liquid samples.
Care must be used in filling the rotor to avoid lubricating the end cap with the sample. If
the end cap is lubricated with the sample the cap could pop off during the experiment. A
very small dot of cyanoacryl ic glue can be u sed to s ecure the end cap. Do not use to much
glue or you will not be able to remove the end cap later.

2.4 Spinning the Sample

W ARNING:

A projectile hazard exists if a spinning rotor explodes. To prevent
possible eye injury from an exploding rotor, avoid spinning rotors
outside the magnet. If it is necessary to spin a rotor outside the
magnet, use a certified safety shield and full face shield at all times.
Never use rotors that have been dropped onto a hard surface, since
microscopic cracks in the rotor material can cause r otor explosions at
much lower spinning speeds than indicated in Table 3 and Table 4.
Never spin zirconia (white) rotors at spinning speeds above 7.2 kHz.
Never spin silicon nitride (gra y) r otors at speeds a bove 9.5 kHz. Never
apply air drive pressure above 72.5 psig (5.0 bar).

W ARNING:

CAUTION:

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

Excessive spinning speeds can cause the rotors to shatter and
explode. Never spin zirconia (PSZ) rotors (white or off-white In
color) above 7.2 kHz or silicon nitride rotors (gra y) above 9.5 kHz.
For samples that have densities above 3.0 g/cc, decrease the
maximum spin rate by 35%.

When removing caps or digging out packed samples, take care not to
gouge the rotor. Even small scratches can imbalance the rotor.

22

Chapter 2. CP/MAS Solids Operation

Introduction

The following applies to spinning the sample regardless of the type of pneumatics/
tachometer box in use. After reviewing these general instructions, see the following
sections for operating instructions that apply to the specific p neumatics/tachometer box that
is installed on your system.

• Pneumatics/tachometer box with rotor spin speed control from within VNMR, see

“Using the Rotor Speed Controller,” page 25.

• Pne umatics/tachometer box with manual spin control, see “Using the Manual

Pneumatics/Tachometer Box,” page 28.

Centrifugal force can cause the b lack and white markings to flake of f around the edges. This
can cause inaccurate tachometer readings. The black or white half circle can be reapplied
on the rotors with a black marking pen and white enamel paint provided in the startup kit.
The diameter marking should be straight.

23

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

2.4 Spinning the Sample

Spinning Rates and Adjusting Bearing and Drive Pressures

Spin rates and the bearing and drive pressures for the Varian CP/MAS probe at ambient
temperature are listed in Table 3 for the 7-mm probe and Table 4 for the 5-mm probe.

Table 3. Typical 7-mm CP/MAS Probe Spin Rates With Bearing and Drive Values

Bearing Drive

Spinning Speed*
(Hz ±250 Hz)

2500 28 (2.0) 12.5 7 (0.5) 15.0
4000 28 (2.0) 12.5 14 (1.0) 20.0
5000 36 (2.5) 12.5 21 (1.5) 25.0
6000 36 (2.5) 12.5 28 (2.0) 27.5
7200 36 (2.5) 12.5 36 (2.5) 30.0
8000 44 (3.0) 10.0 51 (3.5) 35.0
8500 44 (3.0) 10.0 58 (4.0) 37.5
9000 44 (3.0) 9.0 65 (4.5) 40.0

Pressure
psig (bar)

Flowrate
(LPM ±2
LPM)

Pressure
psig (bar)

Flowrate
(LPM ±2
LPM)

*

Rates are approximate values for the Varian 7-mm CP/MAS probe at ambient temperature.

The actual spin rate will vary depending on the properties of the sample and sample holder.

Table 4. Typical 5-mm CP/MAS Probe Spin Rates With Bearing and Drive Values

Spinning Speed *
(Hz ±250 Hz)

4500 28 (2.0) 12.5 7 (0.5) 15.0
7000 28 (2.0) 12.5 14 (1.0) 20.0
11500 49 (3.5) 12.5 35 (2.5) 25.0
13000 56 (4.0) 9.0 63 (4.5) 40.0

* Rates are approximate values for the Varian 5-mm CP/MAS probe at ambient temperature.
The actual spin rate will vary depending on the properties of the sample and sample holder

Bearing Drive
Pressure

psig (bar)

Flowrate
(LPM ±2 LPM)

Pressure
psig (bar)

Flowrate
(LPM ±2 LPM)

For 5-mm CP/MAS probes, spinning a sample with a small amount of drive gas before
applying the initial 28 psig (2.0 bar) of bearing pressure is sometimes useful. The rotor will
begin spinning and will therefore become less likely to flutter (slight motion in and out of
the stator) during initial spin up.

To avoid rotor explosions, never spin 7-mm zirconia rotors faster than 7200 Hz and never
spin 5-mm zirconia rotors in Varian probes. Also, never spin 7-mm silicon nitride rotors
faster than 9500 Hz or 5-mm silicon nitride rotors faster than 15000 Hz.

Overcoming Imbalance

Most of the spinning problems encountered with filled rotors result from imbalance caused
by the sample material. A damaged rotor might be at fault, but that can be eliminated by

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

24

Chapter 2. CP/MAS Solids Operation

always checking the spinning quality of the empty rotor before packing it with the sample
material. Discard damaged rotors . Worn rotor caps can cause imbalance. Changing caps or
rotating them between rotors sometimes cures these problems.

If a packed rotor does not spin properly at first, inspect the sample to see if it has been
disturbed. If part of the sample broke loose and was thrown out of the rotor, repacking the
sample in the rotor might be the solution. Sometimes loos e material balances itself if it is
kept in the rotor and spun belo w its vibration speed for a f e w minutes. If the sample seems
intact on the surface and the rotor is not balanced, it is likely that the sample is not
homogeneous or not evenly packed. The only solution is to remove all the sample and
repack the rotor. W ith inhomogeneous materials, this repacking may have to be tried more
than once. In the case of a machined plug, the plug could have a void in it or it fits too
loosely in the rotor cavity.

Probe Adjust ments for Improved Spinning

Increased bearing pressure often stabilizes samples that do not spin w ell. This adjustment
must be made at low speed and then ramped up once the rotor spinning is st able.

Using the Rotor Speed Controller

The rotor speed controller for Varian MAS probes can be operated with spinning speed
regulation or with a specific airflow setting to control the spinning speed of a sample in a
magic angle spinning (MAS) probe. Alternatively, the air flow can be set to a maximum
(65535) and the dri ve-pressur e regulator on the pneumatics/tachometer box can be used for
manual control the spinning speed.

If the rotor speed controller has not been calibrated, follow the calibration procedures in the
Pneumatics and Tachometer Box Installation manual before continuing.

Chemmagnetics CP/MAS probes use a different speed controller and are not compatible
with this accessory.

Starting the Spinner Speed Controller

1. Enter spinner in the VNMR
input window to open the Spinner
Control window (see Figure 3).

2. Click on the High speed spinner
(solids style) control button.

3. Click on Turn spinner off.

4. If Set spinner airflow instead of
speed is engage d (button press ed
in and red), click on the button to
disengage and set the spinner in
regulation or closed-loop mode.

5. Make sure the drive is set to 0.

6. Set the bearing pressure to 0.

7. Using your fingers, insert an end-cap into the rotor to be spun. Rotate the end cap
while pushing it into the rotor. Make sure the end cap is fully seated into the rotor.

Figure 3. Spinner Speed Control Window

25

8. Carefully place the rotor with the end cap into the stator.

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

2.4 Spinning the Sample

9. Install the probe into the magnet.

10. Set the bearing pressure to a v alue ap propriate for the rotor speed you will be using,
see Table 3 and Tab le 4 for 7 mm and 5 mm rotor bearing pressures.

11. Open the drive value completely.
The rotor may initially spin when using older controllers but will stop when the

electro-pneumatic valve engages.

Regulating Spinni ng Spee d

Direct input of the spinner speed (using the s lider bars in the Spinner Control Windo w, see

Figure 3) uses the closed-loop mode of the spinner s peed re gulation op tion. The s peed can

be increased or decreased by any value and the speed is safely ramped to the new value.
Making small changes in speed (1000 to 2000 Hz) is good practice, until you are
comfortable with the operation and reliability of a particular rotor and endcap combination.

Never exceed the rated speed for any of the rotor parts or probe.

1. Set the slider bar to 2500.
The spinner should regulate to ±2 Hz or better within about 30 seconds to 1 minute.

2. Experiment with a number of set points within the rated speeds of the sample rotor
and probe.

3. Set the desired spin speed using the slider bar.

Regulating Spinning Speed within VNMR

This procedure describes how to regulate spinning speed by entering commands in the
VNMR input window.

1. Start the rotor speed controller as described in the procedure “Starting the Spinner

Speed Controller” on page 25.

2. Click on the but t on next to Allow spin control in an experiment with go.
This button disables the speed in the Spinner Control window and transfers spin rate

control to the spin parameter in VNMR.

3. Set up a typical solids experiment:

a. Set spin to the desired speed.
b. Enter in=’ny’ go.

The spinner regulates at the value of spin. Include a pre-acquisition delay pad to
give the spinner time to stabilize. The parameter spin can be included in an array
to obtain multiple spin rates in a single experiment. In an array of spin, the
pre-acquisition delay is applied before each FID.

4. Click next to Allow spin control in an experiment with go to return control to the
Spinner Control window after the experiment is complete.

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

26

Chapter 2. CP/MAS Solids Operation

Using Air Flow to Set the Spin Speed

This procedure describes how to set the
air flow to spin the rotor. This mode of
operation is applicable when operating at
the extremes of the temperature ra nge of
the probe.

1. Enter spinner in the VNMR
input window to open the Spinner
Control window (see Figure 4).

2. Click on the High speed spinner
(solids style) control button.

3. Adjust the two slider bars to
zero.

4. Click the Set spinner airflow
instead of speed.

5. Click the Turn spinner off button.

6. Adjust the bearing gas pressure to 30 psig for CP/MAS probes.

7. Open the drive pressure regulator fully.
The rotor may initially spin when using older controllers but will stop when the

electro-pneumatic valve engages. The spinner is now in an unregulated mode in
which the airflow is set directly using the slider bar. The slider bar sets the DAC
value that controls the electro-pneumatic value. The DAC has a range of 0 (no air
flow) to 65536 (full open). Only the air flow is set there is no spin speed regulation.

8. Set the slider bar at 2500.

9. If the rotor fails to spin or no DAC reading appears on the tachometer , s top the rotor
and remove it from th e probe, check the paint on the rotor and the tachometer cables.
Repeat this procedure beginning at step 1.

10. Adjust the slider bar until the rotor is spinning at the desired speed.
Move the slider bar slowly. If the rotor is spinning, changing the air flow in small

steps is good practice.
The fine slider bar (b ottom) can be increased by one unit when the mouse pointer is

clicked in the bar. The speed displayed in the Acquisition Status window is correct.
The speed displayed pneumatics/tachometer box tends to be slower.

Do not let a sample rotor exceed the maximum rating for any of the rotor parts
during this process. Speed ratings may vary as a function of temper ature an d sample
density.

Figure 4. Spinner Speed Control Window

27

Using Drive and Bearing Pressure to Control Spin Speed

1. Follow the setup instructions in “Using Air Flow to Set the Spin Speed,” page 27.

2. Reduce the drive pressure until the rotor spinning as a result of the bearing air.

3. Set the slider bars to their maximum position (electro-pneumatic valve is now fully
open).

4. Adjust the drive pressure to achieve the desired rotor spin speed.

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

2.4 Spinning the Sample

Changing Rotors

This procedure describes how to change rotors with MAS probes.

1. Set either the airflow or the rotor speed to zero and click Turn spinner off. Do not
lower the drive-pressure regulator on the pneumatics/tachometer box.

The sample continues to spin at about 200 Hz with the drive air of f. Turn the bearing ­pressure regulator on the pneumatics/tachometer box to zero, and the rotor will stop
spinning.

2. Lower the probe into its stand. The sample rotor can be removed with a small loop
of tape around the index finger.

3. Place the new sample rotor.

4. Raise the probe into the magnet.
Return the bearing pressure to 30 psig (or the desired setting).

5. Set the desired spin speed or air flow.

Using the Manual Pneumatics/Tachometer Box

Table 3 and Table 4 lists spin rates and the appropriate bearing and drive pressures for the

Varian 7-mm and 5 mm CP/MAS probes at ambient temperature. The spin rates shown are
approximate values. The actual spin rate varies depending on the properties of the sample
and sample holder. Use the following procedure for spinning all samples in high-speed
probes:

1. Using your fingers, insert an end-cap into the rotor to be spun. Rotate the end cap
while pushing it into the rotor. Make sure the end cap is fully seated into the rotor.

2. Make sure the bearing and drive air pressure are off.

3. Carefully place the rotor with the end cap into the s tator and install the probe into the
magnet. Turn the air bearing pressure to 28 psig (2.0 bar); the rotor should start
spinning slowly at 500 –90 0 Hz.

4. Slowly turn on the air drive pressure to 3.6 psig (0.25 bar) and wait for 15 seconds
to allow the rotor to stabilize.

5. Gradually increase the air drive pressure to 7 psig (0.5 bar) and again wait 15
seconds. The spinning speed should gradually increase to about 2500 Hz.

6. Slowly increase the air dri ve pressure to 14 psig (1.0 bar). The spinning speed should
reach about 3700 Hz.

7. If rotor speeds faster than 3700 Hz are required, slowly increase the air bearing
pressure to 36 psig (2.5 bar). Then increas e the air drive pressure up to 34 psig (2.4
bar); the rotor speed should reach about 7200 Hz. Never apply air drive pressure
above 72.5 psig (5.0 bar).

To avoid rotor explosions, never spin zirconia rotors faster than 7200 Hz or spin silicon
nitride rotors faster than 9 500 Hz. For samples th at ha v e d ensities abo ve 3.0 g/cc, decrease
the maximum spin rate by 35%.

It may be necessary to increase the bearing p ressure for ill-behaved s amples or for very high
spinning speeds. Provided that the two flowmeter valves are fully open, they require no
adjustment at any time. Never adjust the spin rate with the flowmeter.

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

28

Chapter 2. CP/MAS Solids Operation

Changing Rotors

CAUTION:

To prevent damage to the rotor or bearing, always smoothly shut off
the rotation gas using the rotation pressure regulator before turning
off the bearing gas using the bearing pressure regulator.

1. Decrease the rotor speed smoothly by reducing the drive air pressure.

2. Maintain the bearing air at least 28 psig (1.9 bar).

3. When the rotation air is completely off and the rotor speed has slowed to a few
hundred revolution per second, slowly decrease the bearing air pressure to zero.

4. Lower the probe into its stand. The sample rotor can be removed with a small loop
of tape around the index finger.

5. Place the new sample rotor.

6. Raise the probe into the magnet.

Rotor Synchronization

If the spectrometer is equipped with a rotor synchronization option
(Part No. 00-990385-00), the spinning speed can be read by the acquisition system.

Entering hsrotor='y' su shows the current spinning speed in the acquisition status
window. The parameter srate is updated after each experiment to show the spinning
speed. Furthermore, if in='y', an acquisition is halted if the spinning speed differs by
more than 100 Hz from spinning speed at the start of the acquisition.

For further details on rotor synchronization, refer to the manual System Operation.

2.5 Adjusting Homogeneity

For the balance of this manual, MERCURYcpmas will refer to MERCURY-Vx and
MERCURYplus systems equipped with the CP/MAS option and INOVAcpmas to

UNITY

INOV A and UNITYplus systems with a CP/MAS option. UNITY systems are

described in the previous versions of this manual
Homogeneity should be adjusted as follows on a sample of D

rotor, and tightly capped using a cap with a concentric drilled hole.

1. Insert and seat the sample in the stator.

2. Install the probe into the magnet.

3. Spin the sample slowly (several hundred Hz or less) with 2.0 bar
pressure. A very low drive (rotation) pressure can be used if necessary. Generally,
this slow spinning speed barely registers on the tachometer.

With time, D

4. Enter rt(‘/vnmr/stdpar/H2’) dm=’n’ su.

5. Tune the probe to observe
probe tuning controls. See the Getting Started manual for inst ructions on ho w to tune
a probe.

O spins out of the rotor.

2

2

H by inserting the proper tuning stick and adjusting the

O, prepared in a standard

2

±0.5 bar bearing

29

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

2.5 Adjusting Homogeneity

6. Attach the lock cable from lock preamp to the observe (OBS) connector on the
probe.

System Connector

INOVAcpmas J5205

MERCURYcpmas LOCK PREAMP (J5202) or LOCK PRO B E (J 60 02 )

7. Lock the spectrometer and shim on the lock signal. The principle shims inv olv ed in
adjusting homogeneity when a magic angle spinning (MAS) probe is used are: Z1,
Z2, X, Y, XZ, YZ, XY, and X2Y2.

A typical procedure is:

a. adjust Z1, X, Y, and Z2
b. adjust XZ, YZ, XY, and X2Y2
c. readjust Z1 and Z2
d. adjust any other off-axis shims as necessary

8. To see how well the field homogeneity has been adjusted, do the following:

9. Turn the lock transmitter off by entering lockpower=0 lockgain=0
alock=’u’ su.

10. Disconnect the lock cable from the probe.

11. Connect the cables so that the observe (OBS) port of the probe is connected to the
observe connector on the magnet leg.

System Connector

INOVAcpmas J5311

MERCURYcpmas LO BAND Preamp (J5302) or FROM BB Probe (J6001)

a. Acquire a deuterium spectrum using the deuterium parameter set. The

deuterium linewidth should be typically bet ween 1 and 5 Hz.

b. Finer adjustment and evaluation of the homogeneity is possible using a

sample of solid adamantane (not available from Varian). A linewidth between
2 and 10 Hz is typically attainable, see the sample spectrum in Figure 5.

A solids probe is not lock ed during normal oper ation and Z0 must be adjusted
manually to put the lock on resonance when shimming. When the lock is on
resonance the spectrometer will correctly set the transmitter and decoupler
frequencies. It will be necessary to periodically reset z0 to compensate for
magnet drift whenever you shim. Between shimming sessions it is sufficient
to adjust reffrq, tof and dof.

12. Continue with sect ion “Positioning the Probe and Shimming the D

O FID or

2

Spectrum,” page 30.

Positioning the Probe and Shimming the D2O FID or Spectrum

1. Enter lockpower=0 lockgain=0 rtp(‘/vnmr/parlib/xpolar1’).

2. Enter su.

3. Disconnect the lock cable from the probe.

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

30

Chapter 2. CP/MAS Solids Operation

5.2 Hz at half height
lb = 1.0, at = 0.5

40

30

ppm

Figure 5. Typical MAS Spectrum of Adamantane

4. Reconnect the observe (OBS) por t of the probe to the observ e channel on the magnet
leg.

System Connector

INOVAcpmas J5311

MERCURYcpmas LO BAND Preamp (J5302) or FROM BB Probe (J6001)

5. Enter xpol='n' d1=1.0 nt=1 gain=4 ga.

6. Place the cursor near the D

O resonance and enter movetof.

2

7. Enter sw=5000 ga. Obtain another spectrum.

8. Enter gf acqi.
In the interactive acquisition mode select FID and within this mode select Spectrum.

9. Find the probe position for which changing the z1 shim will not affect the line
position.

a. Observe the spectrum, note the initial value of the Z1 shim and the initial

position of the probe (distance between the base of the magnet and the top of
the probe base or other convenient fixed reverence point).

b. Make a large positive change in the z1 shim.

The D

O resonance may move to positive or negative frequency.

2

c. If the D

If the D

O resonance does not move go to step h.

2

O resonance does move make note of the direction and continue with

2

step d.

d. Loosen the setscrews on the probe flange.
e. Change the height of the probe by a few millimeters (either up or down may

be necessary).
f. Tighten the setscrews and return z1 to the original value.

31

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

g. Make the same large positive change in the z1 shim as in step b. If the D2O

resonance moves again, note the direction and magnitude of the change.

If the change is smaller, continue mo ving the probe in the sam e direction and

repeating steps d through g.

If the change is larger or the same, return the probe and shim to their original

position and value. Move the probe in the opposite direction and repeat steps

b through g.
h. When the D

O resonance no longer changes when z1 is changed, record the

2

height and/or mark the position of the flange on the probe body. Tighten the

setscrews on the probe flange.

10. Repeat step 6 through step 12 of section “Adjusting Homogeneity,” page 29 for the
new probe position. If you interactively fine-adjust the shims and set z0 while
observing the FID or spectrum in step 5 it is not necessary to repeat step 6 through

step 12.

A linewidth of 2 to 3 Hz is typical but 6 Hz is acceptable.

11. Continue with 2.6 “Adjusting the Magic Angle,” page 32.

2.6 Adjusting the Magic Angle

2.6 Adjusting the Magic Angle

Improper adjustment of the magic angle results in incomplete collapse of the chemical shift
anisotropy (CSA) pattern. For carbons with significant anisotropy, such as aromatics and
carbonyls, this can greatly affect the linewidth of the observed resonan ce. In general, once
adjusted, the magic angle should stay fairly constant. Ho we ver, this is not guaranteed. The
angle should be checked and adjusted as follows:

• When the pr obe is inserted in the magnet

• Every few days of continuing operation

• I f linewidths in any particular sample are suspiciously large

Once typical values for the minimum linewidths are established for any particular
instrument, these values can be taken as a reliable indication of proper angle. Adjustment
of the angle is neither necessary nor desirable if the first measurement indicates that the
minimum linewidth has been achieved.

Coarse Adjustment

A convenient method of setting the
sample angle to the approximate magic
angle before final optimization with
NMR is to use the angle measuring
stem (Part No. 00-992825-00) and
angle measuring gauge
(Part No. 00-992826-00) from the
rotor and tool kit. Figure 6 illustrates
how the angle measuring stem and
angle gauge are used.

Figure 6. Coarse Adjustme nt of Sample Angle

54.7°

54.7°

Angle measuring stem

Angle measuring gauge

Probe

Fine Adjustment

The preferred method of adjusting the magic angle uses the 79Br spectrum of KBr, which,

79

when spun at the magic angle results in an extensive set of spinning sidebands. As

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

Br is

32

Chapter 2. CP/MAS Solids Operation

very close in fr equency to 13C, it is easy to switch between the two nuclei. The magic angle
can easily be set or checked as described below.

1. Enter rt(‘/vnmr/parlib/xpolar1’).

2. Enter tn='Br79' to obtain the parameter set to obser ve

3. Load a rotor with KBr, insert it in the probe, and spin it at 3 kHz.
Grinding the KBr crystals before packing the rotor is helpful.

4. Tune the system for
not necessary if the probe is tuned for

5. Enter xpol='n' dm=’n’ d1=0.02 sw=1e5 at=0.02 nt=16 lb=0.

6. Set the following parameter value according to the spectrometer used:

Parameter INOVAcpmas MERCURYcpmas

gain 15 10

7. Enter su.

8. Tune the probe.

9. Enter ga to obtain a spectrum.

79

Br.

79

Br (remove the capacitor stick if it is present) — retuning is

13

C.

10. Set the cursor on resonance, and enter nl movetof.

11. Enter ga to obtain a spectrum.

12. Type df and phase the fid as in Figure 7 and Figure 8.

13. Enter gf.

14. Op en the acqi window, click the FID button, and observe the real-time FID
display.

The FID displays a transient that is an exponential decay with a “picket fence” of one
or more spikes on it (see Figure 7 and Figure 8). If the signal is not exactly on
resonance, repeat step 10 and step 12.

15. Select IPA and adjust phfid to maximize the on resonance FID.

16. Adjust the angle using the fiberglass rod with the adjustment tool.
Maximize the size and number of spikes in the picket fence. The spikes should

persist for about 10 ms. The sample angle is now set to the magic angle.

17. Close the acqi window and retune the probe to

An alternative method of adjusting the magic angle uses
sample, hexamethy lbenzene (HMB), which has tw o

13

C.

13

C CP/MAS of the standard

13

C resonances. Of these, the aromatic
carbon line (on the left side of the spectrum) is extremely sensitive to the angular
adjustment. Figure 9 shows a typical spectrum, including sidebands, of the aromatic
resonance (with lb=0 and good shims). Adjust the aromatic line for minimum lin ewidth
and maximum intensity.

33

Once typical values for the minimum linewidths are established for any particular
instrument, these values can be taken as a reliable indication of proper angle. Adjustment
of the angle is neither necessary nor desirable if the first measurement indicates that the
minimum linewidth has been achieved. T ypical values are 67 Hz for a 300 MHz system and
90 Hz for a 400 MHz system.

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

2.6 Adjusting the Magic Angle

Figure 7. FID Display of KBr on Angle

Figure 8. FID Display of KBr 1/2 Turn Off Angle

HMB Aromatic Carbons

20 0 -20406080100120140160180200

HMB
Methyl Carbons

ppm

Figure 9. Typical Hexamethylbenzene (HMB) Spectrum

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

34

Chapter 2. CP/MAS Solids Operation

2.7 Calibrating the CP/MAS Probe

Calibrating 13C Nucleus Pulse Width

The following steps cover calibrating the pulse width.

1. Insert a rotor containing liquid-state p-dioxane and spin at 200-300Hz.
Do not spin faster than 200-300 Hz, or the p-dioxane will be forced out of the hole

in the rotor cap. The addition of a small amount of CrAcAc (not provided) to the
p-dioxane will allow you to use d1=1.0 in these tests.

2. Recall the parameters by entering rt('/vnmr/parlib/xpolar1’).

3. Enter tn=’C13’ reffrq=sfrq d1=10 nt=4 xpol='n' at=0.05
lb=10.

4. Set the following parameter values according to the spectrometer used:

Parameter INOVAcpmas

gain 40 40 20
tpwr 63 54 63
tpwrm 1600 1600 100
dpwr 63 55 63
dipolar 1600 1600 100

INOVAcpmas

(1 kW amplifier)

MERCURYcpmas

5. Enter su.

6. Tune the probe to

13

C for p-dioxane.

See Getting Started for instructions on how to tune a probe.

7. Enter ga.

8. Place the cursor 500 Hz on low field side of the p-dioxane resonance and enter
movetof.

9. Enter sw=5000 ga.

10. Array pw from 0 to 5 times the 90

11. Increase tpwrm as necessary to achie ve the 90

o

pulse width. Do not exceed the 90o pulse width specification.

90
If you cannot achieve the

13

o

pulse width specification.

o

pulse width specification or desired

C 90o pulse width specification with tpwrm set to full
value, you may need t o r emove any attenuation added to the lo wband amplifier and
repeat the calibration.

13

12. Record the values of tpwr and tpwrm used to obtain the

C 90o pulse width

specification. Save the final data for reference.
Estimate the

difference between the 360
measurement of twice the 90

13

C 90o pulse width using either use the maximum 90o or find the

o

and 180o and divide by 2. The 180o is not a good

o

because of r.f. inhomogeneities of the coil.

13. Continue with “Calibrating Decoupler Power,” this page.

35

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

2.7 Calibrating the CP/MAS Probe

Calibrating Decoupler Power

Using the previously determined pw, calibrate decoupler power (γB2) as follows.

1. Recall the parameters used in the previous test.

2. Set pw, tpwr, and tpwrm to the values obtained for the
specification in “Calibrating

13

C Nucleus Pulse Width,” page 35.

3. Enter dof=5e4,-5e4 d1=10 xpol=’n’.

4. Enter at=0.05.

5. Set the following parameter values according to the spectrometer used.

Parameter INOVAcpmas

dpwr 63 55 63
dipolar 4095 4095 255

INOVAcpmas

(1 kW amplifier)

6. Enter ga.

7. When acquisition is finished, measure the reduced coupling on each of the two
spectra.

13

C 90o pulse width

MERCURYcpmas

8. Enter h2cal to calculate
This is the maximum decoupler power,

γB

Max fails to meet specifications, remove some of the attenuation from the input

2

to the highband amplifier and repeat the

9. Calculate the

a.

γB

CP (1H cross polarization field):

2

γB

CP=1.0/(4.0*13Cpw90) where 13Cpw90 is the value determined in the

2

γB

.

2

γB

Max. Record this value. If the value of

2

γB

Max calibration.

2

previous section.
b. Adjust dipolr and enter ga.
c. Repeat step 6 and 7.

γB

d. Adjust the value of dipolr until the value for

measured in 7 equals the

2

value calculated in step 8a.
e. Record the values of dipolr and

γB

CP. These values will be used in the

2

next section.

10. Continue with “Adjusting the Hartmann-Hahn Match,” this page.

Adjusting the Hartmann-Hahn Match

Hartmann-Hahn matching can be readily accomplished by using a sample of
hexamethylbenzene, HMB.

1. Load a rotor with HMB, insert it in the probe, and spin it at about 2500 Hz.

2. Recall the test parameters by entering rt('/vnmr/parlib/xpolar1').

3. Enter xpol='y'.

4. Set pw, and tpwr to the values obtained for the

13

C pw90 in “Calibrating 13C

Nucleus Pulse Width,” page 35.

5. Enter dpwr dipolr and dof values determined in “Calibrating Decoupler

Power,” page 36.

1

Use the second set of values for the

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

H cross polarization field.

36

Chapter 2. CP/MAS Solids Operation

6. Enter crossp=dipolar cntct=2500 at=0.02 d1=1 nt=4 sw=45000 .

7. Set the following parameter values according to the spectrometer used.

Parameter INOVAcpmas

gain 40 40 20
tpwr 60 54 63
tpwrm array(‘tpwrm’,40,95,100) array(‘tpwrm’,52,0,5)

8. Enter lb=50 ga.

9. When acquisition is finished, enter dssh to display the results.

10. Select the spectrum with the lowest value of tpwrm that gi v es the maxi mum s ignal
and set tpwrm to the value of this spectrum.

11. Optimize pw.

a. Array pw from 0 to 2 times its current value.
b. Enter d1=1 ga.
c. When acquisition is finished, enter dssh to display the results.
d. Select the spectrum with the maximum signal and set pw to this value.
e. Enter ga.
f. Save this spectrum for reference.

INOVAcpmas

(1 kW amplifier)

MERCURYcpmas

12. Continue with “Measuring Signal to Noise,” page 37.

Measuring Signal to Noise

1. Use the parameters and the value of tpwrm from “Adjusting the Hartmann-Hahn

Match,” page 36.

2. Enter d1=5 nt=4.

3. Enter ga.

4. Set delta=10000 and place cursor at the right edge of the spectrum and enter
dnsmax to measure the signal to noise.

5. Compare the signal to noise to the specifications.
If necessary , increa se the gain and repeat step 2 through step 4. Do not overload the

ADC.

6. Repeat step 2 and step 4 three times and record the signal to noise for each test.

7. Record the average signal to noise for the system.

2.8 Referencing a Solids Spectrum

A solids probe is not locked during operation. If exact chemical shifts are required, a
spectrum of a test sample with know chemical shift must be obtained. The HMB
signal-to-noise sample can be used for this purpose.

37

1. Obtain a spectrum of HMB using the parameters that gave the best spectrum in 2.7

“Calibrating the CP/MAS Probe,” page 35.

2. Enter cr=100p movetof.

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

2.9 XPOLAR1—Cross-Polarization

The transmitter is placed in the center of the spectrum.

3. Enter ga.

4. Put the cursor on the tall methyl line and type nl rl(17.43p) ga.
The reference (reffrq) is

set only after you use the rl

Table 5. Reference Materials and 13C Chemical

Shifts

command to reference. If you
change tn without using rl

Substance Chemical shift (ppm)

the chemical shift scale and
reference will be that of the
previous nucleus. The new
reference (reffrq) is sav ed
with the data only after you
type ga. If you do not acquire
a new spectrum you will
reference only the display

adamantane 29.2, 38.3
delrin 88 .5
glycine 43.6, 176.4
hexamethylbenzene 17.3, 132.1
poly(methyl methacrylat e) 19, 45, 51, 176
talc (29Si) –90

(rfl and rfp) in the current
experiment.

5. Save the HMB data set and use it as the starting point for all solids spectra until you
re-reference.

The frequency of re-referencing depends upon the drift rate of your magnet. A drift rate of
10 Hz per hour is 2.5 Hz per ho ur for

13

C. A typical 13C linewidth of a solid is between 30

Hz and 300 Hz.
For most purposes, this procedure should be followed only at the time the probe is installed.

13

C chemical shifts of a few reference materials are given in Table 5.

The

2.9 XPOLAR1—Cross-Polarization

XPOLAR1 is applicable to MERCURYplus, MERCURY-VX,
newer UNITY systems. The parameters that control the attenuators and linear modulators
are shown in the diagram of XPOLAR1, see Figure 10.

cntct

(tpwrm)

Tx

pw

d1

cntct

(crossp)

UNITY

at

(dipolr)

INOVA, UNITYplus, and

Dec

AC

Figure 10. XPOLAR1 Pulse Sequence

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

38

Chapter 2. CP/MAS Solids Operation

Cross-polarization amplitudes should be controlled using the fine attenuator. The fine
attenuator has a range of 60 dB for Ino va and 48 dB for MERCURY systems down from the
course attenuator. The coarse attenuator is set to a value corresponding to the maximum
specification of the probe. Cross-polarization on the UNITY requires the use of both the
coarse and fine attenuators (6 db range).

Applicability

XPOLAR1 can be found in /vnmr/psglib. The MERCURYplus and MERCURY-VX

UNITY

version of XPOLAR1 is not interchangeable with XPOLAR1 for

INOVA and
UNITYplus systems. UNITY systems can use both XPOLAR1 and XPOLAR by setting
dblvl2=’y’.

Macro

When this macro is run on a
convert s parameters for XPOLAR and most ot her double- and triple-resonance solids pulse
sequences for the XPOLAR1 pulse sequence. Power parameters are left unchanged.
Parameters irrele vant to XPOLAR1 are remo ved. On MERCURY-VX or MERCURYplus the
macro XPOLAR1 will convert parameters contained in experiments run on
UNITYplus, and UNITY when these data sets are loaded on the system and the macro is
run.

For users familiar with
following:

• If the UNITY power parameters are defined (in an XPOLAR parameter set),
they are converted to the corresponding
parameters: (level1=cppwr level2=dpwr level1f=crossp
level2f=dipolr p2=cntct tpwrf=tpwrm) and dblvl2 is set to 'n'.
If dblvl2=’y’, both cppwr and dpwr are used. If dblvl2=’n’, cppwr is not used
and dpwr=cppwr.

• xpolar1 does not convert an arbitrary parameter set for solids. First retrieve a
solids parameter set (e.g., xpolar.par in the VNMR directory parlib) and
then convert it with the xpolar1 macro.

UNITY

INOV A, UNITYplus, and UNITY, the macro xpolar1

UNITY

UNITY

INOVA, UNITYplus, and UNITY solids, note the

UNITY

INOVA and UNITYplus

INOV A,

39

Parameters

• xpol is set to 'n' for direct polarization or xpol is set to 'y' for cross- polarization.

• pw is the observe pulse for direct polarization, or the proton 90
polarization. pw is in microseconds.

• pwx is th e obser ve 90

o

pulse, used for TOSS and dipolar dephasing, pwx is in

microseconds.

• cntct is th e cross-po lar ization contact time, in microseconds.

• tpwr is th e obser ve power setting .

Spectrometer Minimum, dB Maximum, dB

INOVAcpmas -16 63
MERCURYcpmas 063

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

° pulse for cross-

2.9 XPOLAR1—Cross-Polarization

• tpwrm is th e observe linear modulator setti ng .

Spectrometer Minimum Maximum

INOVAcpmas 0 4095
MERCURYcpmas 0 255

The parameter tpwrm is linearly proportional to the applied transmitter voltage—
doubling tpwrm halves the value of the pulse width.

• dpwr is the decoupler power setting for decoupling throughout the acquisition period .

Spectrometer Minimum, dB Maximum, dB

INOVAcpmas -16 63
MERCURYcpmas 063

• cppwr (UN ITY only) is th e decoupler power setting for cross polarization when
dblvl2=’y’.

• dipolr is the decoupler linear modulator setting during acquisition (0 minimum
voltage to 409 5 for INO VA or 255 for MERCURY series maximum voltage). The value
of dipolr is linearly proportional to the applied decoupler voltage—doubling
dipolr doubles the decoupler field strength (in kHz).

• dblvl2 (UNITY only) is set to ‘y’ to obtain the parameter cppwr.

• crossp is the decoupler lin ear modulator setting during cross-polarization and the
initial 90

° pulse (0 minimum voltage to 4095 for INOVA or 255 for MERCURY serie s

maximum voltage). The range is similar to dipolr. Doubling crossp doubles the
cross-polarization field strength (in kHz) and halves the initial proton 90

° pulse.

• p180 greater than 0.0 implements an additional prepulse, followed by a delay d2. For
direct polarization (xpol='n'), p180 is an observe pulse. For cross-polarization
(xpol='y'), p180 is a proton pulse. p180 is in microseconds.

• pcrho greater than 0.0 implements an additional observe pulse following the contact
time. Use pcrho for observe T

measurements. The units for pcrho are

1ρ

microseconds.

• dm should be set to 'nny'. The decoupler has a maximum duty cycle of 20%.

• pdp set to 'y' im plements interrupted decoupling for a period pdpd2 to cause
suppression of protonated carbons.

• pdpd2 is set greater then 0.0 (see pdp), pdpd2 is in microseconds

• d2 is set greater than 0.0 (see p180), d2 is in seconds.

• srate is th e sam ple spinn in g speed, in Hz.

• hsrotor set to ‘y’ allows automatic update of the value of srate if automatic
spinning speed control is used.

• toss set to 'y' implements timed spin echoes to suppress spinning side bands.
Timing is determined from the value of srate.

Note that for toss='y' or pdp='y', srate must be set correctly because delays
are calculated from 1.0/srate.

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

40

Chapter 2. CP/MAS Solids Operation

2.10 Optimizing Parameters and Special Experiments

This section provides information on parameters used for specific optimizations, such as
contact time and repetition rate. Also included in this section are special experiments for
the high-performance CP/MAS module. With each of these experiments is a sample
spectrum and an illustration of the XPOLAR1 pulse sequence used.

Contact Time Array

For samples in which cross-polarization is used, the contact time, that is, the time during
which cross-polarization occurs, must be optimized with the parameter cntct. This is
necessary because two processes are occurring simultaneously:

• Build -up of magnetization due to cross-polarization

• Los s of magnetization due to rotating-frame relaxation

A time exists for which an optimum
in the magnetization occurs.

The optimum cntct can lie
anywhere from 100 to 5000
Generally the optimum value is
similar for a class of compounds,
but for new types of sample s an
optimization of cntct is highly
desirable. Figure 11 shows a typical
optimization. Note that a
simultaneous optimum for all
carbons in a spectrum does not
necessarily occur. A value of 1000

µs is adequate for protonated carbons and crystalline solids. A value of 3000 µs is needed

for non-protonated carbons and solids with internal motion.

µs.

Figure 11. Array of Contact Times

41

Optimizing the Repetition Rate

Acquisition times in CP/MAS spectra are determined by the desired sp ect ral resolution.
T ypically , set sw=50kHz. W ith at=0.05, this gives at least 2048 data points and a digital
resolution of 4 Hz, a reasonable value.

The repetition rate is determined by the parameter d1, the delay between experiments. CP/
MAS spectra are acquired with 90
is 1.25*T
xpol=’n’, it is the T
liquids. A t 300 MHz, a d1 of 5 seconds is usually acceptable for polymers; at 400 MHz,
10 seconds can be better.

. For cross-polarization spectra, this T1 is the value of the protons; for

1

of the carbon or other nucleus. T1 values can vary widely, as in

1

° observe pulses. In this case, the optimum repetition rate

Suppressing Spinning Sidebands

NMR spectra of solids at high magnetic fields often have significant spinning sidebands.
While these sidebands contain information about the chemical shift anisotropy, they can
complicate the interpretation of complex spectra. The sidebands can be eliminated using
the TOSS (TOtal Sideband Suppression) technique. The TOSS pulse sequence is selected
by setting toss='y' in the XPOLAR1 sequence (see Figure 10). Note that the parameter
srate should be set to the spinning speed in Hz.

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

2.10 Optimizing Parameters and Special Experiments

TOSS is less effective at high spinning speeds. Note that if suppression is not complete,
check that srate is correct. TOSS uses 180

° pulses based on pwx. It may b e necessary to

adjust pwx to optimize the TOSS experiment.

toss='y'

toss='n'

xpol='y' toss='y'

cnctct

pw

(crossp)

dipolr

d1

13

1

H

cntct

(tpwrm)

C

2*pwx

Delay recipe
including srate

Figure 12. TOSS Experiment on Alanine (Spectrum and Sequence)

Suppressing Protonated Carbon (Interrupted Decoupling)

Off-resonance decoupling and related experiments in which J-coupling is involved are not
routinely possible in solids because dipolar coupling as well as J-coupling is present. One
experiment exists, however , that is used in solids to discriminate between carbon types, and
that is the protonated carbon suppression experiment of Opella and Fry. In this experiment,
the decoupler is turned off for 40 to 100
carbons.

The technique is effective primarily for non-mobile carbons; mobile carbons, like methyl
groups, are typically not suppressed as well. Figure 13 shows a typical protonated carbon
suppression experiment on alanine, obtained by setting pdp (protonated dephasing) equal
to 'y', setting srate to the spinning speed, and entering appropriate values for pdpd2

µs), the dephasing time.

(in

µs before acquisition to dephase the protonated

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

42

Chapter 2. CP/MAS Solids Operation

xpol='y' pdp='y'

pw

d1

1

H

cntct

(crossp)

pdp='y'

pdp='n'

(dipolr)

13

tpwrm

C

pdpd2

1/srate

2*pw

1/srate

Figure 13. Protonated Carbon Suppression of Alanine (Spectrum and Sequence)

13

C T1ρ Experiments

Measurements of the spin-lattice relaxation time in the rotating frame (Tlρ) are possible
using the standard XPOLAR1 pulse sequence. Anytime that pcrho is set to a non-zero
value, a T
Typical values for pcrho would range from 50 to 5000

To analyze a T

decay is introduced; thus, by setting pcrho to an array, Tlρ is measured.

lρ

µs.

experiment for the decay time constant, enter

lρ

analyze('expfit','pcrho','t2','list')

In experiments other th an T

experiments, pcrho should be set to 0. Figure 14 sho ws the

lρ

spin-lattice relaxation measurement pulse sequence.

pw

xpol='y'

cntct
(crossp)

(dipolr)

43

d1

1

H

13

cntct
(tpwrm)

C

pcrho

(tpwrm)

Figure 14. Rotating-Frame Spin-Lattice Relaxation Measurements Sequence

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

2.11 Useful Conversions

1

H T1 Through 13C Cross-Polarization

l

H T1 can be measured using the XPOLAR1 pulse sequence by setting it up to perform a
standard inversion-recovery experiment on the protons followed by cross-polarization of
the remain

1

H magnetization to the carbons. Figure 15 illustrates the pulse sequence.

xpol='y'

13

d1

1

H

C

p180

Figure 15. Pulse Sequence for Measuring lH T

2.11 Useful Conversions

Convert from 90° pulse width to γH:

250

γH2kHz()

Convert from field strength in gauss to field strength in gauss:

1

H: γH (kHz) ≈ 4.3 * γH (gauss)

13

C: γH (kHz) ≈ γH (gauss)

Convert from rf fields to power levels:

P (watts)

-------------------------------------­90°pulsewidth

2

∝ (γH)

pw

d2

µs()=

cntct

(crossp)

cntct

(tpwrm)

(dipolr)

1

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

44

Chapter 2. CP/MAS Solids Operation

45

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

Chapter 3.

Sections in this chapter:

• 3.1 “Wideline Solids Module,” this page.

• 3.2 “Wideline Experiments,” page 50.

• 3.3 “SSECHO Pulse Sequence,” page 51.

• 3.4 “Data Acquisition,” page 51.

• 3.5 “Standard Wideline Samples,” page 53.

• 3.6 “Data Processing,” page 55.

Unnarrowed spectra of solid samples can often reveal a great amount of information. In
wideline NMR, no attempt is made to narrow the resonances (as done by CP/MAS), and
patterns up to 0.5 MHz or wider can occur.

As lineshape is of the utmost importance, the spectrometer must be able to measure very
broad lines without any distortion. It is for this reason that the transmitter power is high.

γH1 must be large enough to uniformly excite the entire spectrum. (The effects of a finite

° pulse width may be investigated with simulations using the solids analysis software

90
accessory.) With linewidths in excess of 100 kHz, an increase in ADC speed is necessary.
In fact, the typical spectral widths used often greatly exceed the linewidths because many
spectra are obtained under over-digitized conditions.

Wideline Solids Module Operation

3.1 Wideline Solids Module

The wideline module for the V arian spectrometer modifies and extends the basic capability
of the system in a number of areas. The main components of the wideline module are the
wideband ADC, high-power amplifier, and the solids cabinet.

Wideline ADC Board

A wideline analog-to-digital con v ersion (ADC) boar d is added to the system in addition to
the standard ADC board. Based on the spectral width (the parameter sw), the software
determines which ADC board is to be used—values of sw greater than 100 kHz will
automatically use the faster ADC.

Two versions of the wideline ADC board exist:

• The newer version of the Wideline ADC board (Part No. 00-993350-00) was shipped
with UNITYplus systems. It has its own on-board memory, which consists of 2 x 64
Kword buffers (maximum np is 131072), together with its own sum-to-memory
(STM) circuitry. Data is summed at this speed without additional overhead. This bo ard
also contains a Bessel filter, either 256 kHz (6-pole Bessel) or 1 MHz (4-pole Bessel).
This filter is switched in when sw is less than 256,000 Hz; otherwise, the 1 MHz filter
on the receiver is used.

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

46

Chapter 3. Wideline Solids Module Operation

• The older Wideline ADC board was shipped with U NITY and VXR-S systems. It
acquires data in a fundamentally di f ferent manner. Data is temporarily stored in its on­board, 2 x 8 Kword buffer (maximum np is 16384). After each FID is collected, data
is transferred to the normal acquisition memory and the fast memory is cleared. This
process requires an overhead of about 32

Both ADC boards are single VERSAbus boards containing sample-and-hold modules,
ADC chips, memory, and control logic, and each board is capable of digitizing 12 bits in
500 ns. The ADC conversion time is adjustable in 25 ns steps, so there are only a limited
number of actual values that the spectral width can take. The entered value of sw is
automatically adjusted to the nearest valid spectral width.

The standard Observe Receiver board for
correct bandwidth amplifier and is not replaced. For UNITY and VXR-S systems, the
Wideline Receiver and Filter board is a replacement of the standard 100 kHz receiver and
contains filters appropriate for both small and large spectral widths. Improved filters give
better baseline and phase characteristics; however, they may show a 10% reduction in
signal-to-noise as determined by the standard

µs for each complex point.

UNITY

INOVA and UNITYplus systems ha s the

13

C test.

For spectral widths above 100 kHz, 6-pole true

Table 6. Bessel Filter Ou tputs

Bessel filters are used. The outputs from these
filters are routed to the wideband ADCs. The
permissible values of the parameter fb, which are
identical to the 3 dB points of these filters, are
listed in Table 6.

For 100 kHz and below, the signal is routed
through a pair of 8-pole quasi-elliptical filters to
standard ADCs. The characteristics of these filters
provide superior performance for both phase and
amplitude flatness across the full spectral width.

UNITY

The Wideline NMR Module for the

INOV A

sw (kHz) fb (kHz)

100 – 225 256
> 225 1000
300 – 540 300
540 – 1260 700
1260 – 1800 1000
> 1800 2400

system is a board that includes two 5-MHz 12-bit ADCs and 2 MB of onboard memory.

High-Po wer Amplifier

The wideline high-power (1 kW) amplifier is intended mainly for use in solid-state NMR
studies. The amplifier is housed in a third cabinet, as shown in Figure 16, and configured
to permit maximum flexibility. Manual controls permit selection of either the solids
amplifier or the standard liquids amplifier for the observe function.

CAUTION:

Never use probes designed for liquids studies with amplifiers intended
for solid-state studies. The high power from these amplifiers will
destroy liquids probes.

47

Because the wideline package is for low-band (12 to 200 MHz) nuclei, no 1H or 19F high­power amplifier is provided unless the CP/MAS module or CRAMPS/Multipulse module
is also installed. The 1-kW power amplifier is one of the following models:

• The AR Model 1000LPM10 covering the range of 9 MHz to 200 MHz with 60 dB of
gain and a maximum output power exceeding 60 dBm over this range.

• The AMT Model M3201 covering a range of 6 MHz to 220 MHz with 10 dB of gain
and a maximum power output exceeding 60 dBm over this range.

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

3.1 Wideline Solids Module

Status panel

Sorensen Solids
VT controller (optional)

Low band 1 kW
amplifier

Low band
power supply

High band 1 kW
amplifier

High band
EHT power supply

Figure 16. Solids Cabinet Layout, Open Front View

Both amplifiers are linear, with gating provided for noise blanking. Operational details for
the high-power amplif iers are included in the manuals pro vided by the manufactur ers of the
amplifiers. These should be read before operating the amplifier.

AR Linear Amplifier

The AR linear amplifier is gated of f whene v er the recei ver is gated on. A time o f at least 30

µs is required for the bias to come on fully and thus for the amplifier to provide full output

power. Allowance for thi s de lay mus t be made in any pulse sequence programming, using
rof1. The amplifier can be driven in either of two modes:

• Continuous wave (CW)—the maximum power output is limited to 200 W but the duty
cycle can be 100%

• Pu lsed — the maximum power output is 1 kW but the maximum pulse width is 8 ms
with a maximum duty cycle of 10%.

The amplifier is fully protected against thermal overload, excessive duty cycle, and
excessiv e pulse width. Status lights on the front panel and s witches for this unit are v isible
by opening the front door of the third cabinet.

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

48

Chapter 3. Wideline Solids Module Operation

Although you should study the AR manual before using the amplifier, an abbreviated set of
operating instructions are given here (words in all capital letters refer to controls on the
front panel).

The gating input to the amplifier is of positive lo gic, with a 5 V on an d 0 V o ff signal. The
amplifier is class A with noise blanking in the CW mode. In the pulsed mode, the amplifier
operates class AB and the gating input acts as a gating signal. When gated off, the output is
greatly attenuated.

• To operate in the continuous mode, turn on the POWER button, wait for the
STANDBY button to light, then press the OPERA TE button. In the continuous mode,
the gating signal input should be disconnected at the AR front panel.

• To operate in the pulsed mode, press the OPERATE button to set the amplifier in the
standby mode. Press the PULSED button, then the OPERATE button once again. The
amplifier is now in the pulsed mode, with pulse gating, not noise blanking. The
maximum rated power output in the pulsed mode is 1 kW (60 dBm). This should not
require adjustment of the amplifier gain.

• To return to the continuous mode, switch back to the standby mode by pressing the
OPERATE button, followed by powering off the amplifier.

The AR amplifier has been calibrated at 100 MHz so that when its front panel gain control
is set to the marked position and the manual attenuators are set to 0, the power output is
equal in dBm to the v alue of tpwr, in other words, tpwr=60 delivers 1 kW (60 dBm) and
tpwr=50 delivers 100 W (50 dBm). This calibration may not be precise at other
frequencies, but provides a first approximation.

AMT Linear Amplifier

The AMT linear amplifier is gated of f whene v er the receiver is gated on. A time of at least

µs is required for the bias to come on fully and thus for the amplifier to provide full output

8
power. Allowance for this time delay must be made in any pulse sequence programming,
using rof1.

The maximum pulse width is 20 ms at full outpu t and with a maximum duty cy cle of 10%.
The AMT amplifier is fully protected against thermal overload and it indicates excessive
duty cycle and excessiv e pulse width. Status lights on the front panel and the power switch
are visible inside the front doo r of the third cabinet as well as on the status panel. The gating
input to the amplifier is of positive logic, with a 5 V on and 0 V off signal.

CAUTION:

Never operate a high-power amplifier unless terminated by an
appropriate 50-ohm load.

Decoupler Amplifier

The three possibilities for the decoupler amplifier in wideline systems are as follows:

• Standard decoupling operation.

• 100 W CP/MAS decoupler—operation of this is the same as for CP/MAS.

• 1 kW decoupler amplifier.

Status Panel

49

The high power amplifiers are controlled by a status panel.
The HI POWER ENABLE subpanel contains two switches:

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

3.2 Wideline Experiments

• The OFF button grounds the inputs of both high power amplifiers and routes the
transmitters through the standard
appropriate for liquids operation (note that both amplifiers are left po wered up by this
switch).

• If HI POWER ENABLE is OFF, the position of the HI POWER/LO POWER switch
is immaterial—the high-power amplif iers cannot re ceive any rf drive . The ON switch
activates the cabinet, enabling the HI POWER/LO POWER toggle switches.

Observe Transmitter

For both the solids and standard liquids channels, the computer-controlled attenuators are
in-line. The power lev el is controlled by the parameter tpwr in 1 dB incremen ts from –16
to 63 dB stan dard (0 to 63 dB is standard on UNITY and VXR-S systems). Maximum
power output is obtained with tpwr=63. T o get lo w pow er from the hig h-power amp lifier ,
tpwr should be decreased by approximately 6.

Note that the output of the Observe Transmitter board can be routed to a low-power (300
W) amplifier (LOW POWER position on the third cabinet, see Figure 16) or to a high­power (1 kW) amplifier (HI POWER position).

3.2 Wideline Experiments

Wideline NMR experiments can be divided into three main areas, based on spin quantum
number (I). The experiments possible are certainly not restricted to just one of these
categories, but are normally used in one group rather than in all. Table 7 lists command s
and parameters related to wideline experiments.

UNITY

INOVA, UNITYplus, and UNITY electronics

Table 7. Wideline Experiment Commands and Parameters

Commands

ssecho Set up solid-state echo pu lse sequence
tmove Left-shift FID to time-domain cursor
tshift Adjust tau2 to current cursor position

Parameters

dotflag {'y', 'n'} Display FID as connected dots
lsfid {number, 'n'} Number of complex points to left-shift np
scalesw {number > 0.0, 'n'} Scale spectral width in directly detected dimension

Dipolar Nuclei (I = 1/2)

The most common dipolar nucleus is 1H. Many of the dipolar nuclei are not usefully
observed under wideline cond itions without
wideline probe does not allow double-resonance experiments, a CP/MAS probe can be
used for many such experiments.

1

H wideline experiments, lineshape or chemical shift is usually of minor importance.

In
The most interesting parameters are relaxation rates such as T
measurements the relevant part is the first few micros econ ds of the FID. The FID may not
even be transformed.

1

H decoupling. Although the standard

, T2, and T

1

. In many

ρ

1

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

50

Chapter 3. Wideline Solids Module Operation

Normally the breadth of a line comes from two sources, dipolar couplin g and chemical shift
anisotropy. There are a number of techniques, referred to as line narrowing, or multipulse
techniques, to remove dipolar coupling contributions to lineshape.

Quadrupolar Nuclei (I = 1 or 3/2)

For all quadrupolar nuclei, the main cause of linewidth is the quadrupolar coupling of the
nuclei being observed. The observed magn itude of the qu adrupolar coupling is dependent
on orientation in the magnetic field and is res pon sib le for th e appar ent difference between
single crystal and powder spectra.

The most commonly observed quadrupolar nucleus in wideline is

23

Na and a few other nuclei. Lineshape is of prime consideration in most experim ents

with
involving these nuclei, with relaxation measurements also of interest.

To ensure an accurate representation of the lineshape, most spectra are measured via an
echo sequence, first described by Mansfield (Phys. Rev.,
known as the “solid echo” sequence. To simplify phasing of the transformed FID, the echo
is Fourier transformed from the top onwards in time. The “extra” data points are ignored
using lsfid. To accurately define the echo top, these echoes are usually over-digitized.

2

H (deuterium), along

137, A961, (1965)), commonly

Quadrupolar Nuclei (I > 3/2)

Quadrupolar nuclei are also observed via echo sequences; however, as different types of
lineshape information may be sought, a number of different echo sequences may be used,
depending on the quantum transitions of interest (I. D. Weisman and L. H. Bennett, Phys.

Rev., 181

, 1344, (1969)).

3.3 SSECHO Pulse Sequence

One basic pulse sequence, SSECHO, is provided to support quadrupolar wideline
experiments. This pulse sequence can perform conventional “solid echo” ex periments, with
or without composit e pulses. It also supports inv ersion- recovery solid echo e xperiments , as
well as echo experiments with unequal pulse widths. The details of this pulse sequence are
discussed in Chapt er 6, w hich also prov ides a mo del for users for w hom other v ariations of
the experiment may be of interest. Since this pulse sequence, like all others, undergoes
periodic revision and impro vement, you are encouraged to print the v ersion current in your
software with the ptext command: ptext('/vnmr/psglib/ssecho.c'). The
SSECHO pulse sequence is not appropriate for proton relaxation studies.

3.4 Data Acquisition

For data acquisition, consider sample preparation, shimming, and pulse-width calibration.

51

Sample Prepar ation

The main requirement is that the sample be no longer than 25 mm nor greater than 5 mm
in diameter. Samples must fit into the coil of the probe and be electrically insulated from
the coil. The most convenient sample carrier is a 15 mm length of 5 mm outside diameter
NMR tube, which can be sealed with P arafilm or some other backg round-free materi al. For
best results, the sample should be kept small in comparison with the length of the coil and

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

3.4 Data Acquisition

should be placed symmetrically in the coil when in the probe. Remember that the NMR

29

tube has a

W ARNING:

Si, (l3Na)27Al and 11B background signal.

Dangerous high voltage exists inside the probe that can cause burns
or serious injuries. Follow the instructions below to avoid the hazard.

When changing samples, take the following precautions:

• Set the HI POWER ENABLE switch to OFF.

• Disco n nect the transmitter cable from the probe.

• Be especially careful of damaging the coil supports when inserting or removing a
sample from the coil as well as when changing coils. These supports are fragile and
can be easily damaged.

Shimming

Because of the width of the resonances encountered in wideline work, shimming is rarely
necessary (or possible!) on each sample. The following approach is typical:

1. When the probe is first installed, insert a sealed sample of D
shimming purposes.

2

2. Tune the probe to

H, as described in the probe installation manual, and then connect

the (otherwise unused) lock cable to the observe channel of the probe.

3. Use the interactive acquisition window to lock the spectrometer in the usual way , and
then adjust the important shims. Usually it is only important to adjust X, Y, Z1
Coarse, and Z2 Coarse.

O in the probe for

2

4. When finished shimming, turn the lock off and adjust Z0 so that the lock signal is
on-resonance. This ensures that the field will be in the same position as used for
liquids work, so that the usable frequencies will be the same.

5. Set lpower=0. This ensures that at the time of the next su command, the lock
transmitter is deactivated, removing a source of potential frequency interference.

Pulse-Width Calibration

Although it is possible to perform pulse width calibrations on the sample of interest using
solid-state echo experiments, calibrations done in this manner can be misleading. For
example, there is not usually a null at the 180
rule, all pulse width calibrations should be made with solutions. A sample of D

2

used for
as

H work, while a 1 M solution of a salt in water can be used for other nuclei such

23

Na.

The acquisition controller board of the
limits your ability to specify a pulse width to increments of 0.0125
UNITYplus and UNITY have a timing resolution of 25 ns, thus limiting pulse width
specification to increments to 0.025
will alter the 90
used with

° pulse width parameter pw90. In addition, the parameter tpwrm can be

UNITY

INOVA and UNITYplus systems.

µs. Adjustment of the power with the parameter tpwr

° pulse for quadrupolar nuclei. As a general

2

UNITY

INOVA has a timing resolution of 12.5 ns, which

µs. Similarly, the

O can be

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

52

Chapter 3. Wideline Solids Module Operation

3.5 Standard Wideline Samples

Two standard wideline samples are provided with the system, malonic acid-d4 for 2H and

23

sodium nitrate for

Na wideline NMR. These samples are provided as an aid to becoming
familiar with the operation of the wideline module and do not have any associated
specifications.

Obtaining a Wideline Spectrum of Deuterium

The deuterium powder pattern spectrum of malonic acid-d4 can be obtained in the
following manner (this is not the only way to operate the wideline module, but does provide
a convenient starting point):

1. Determine the 90

° pulse using a solution, in this case, 2% D

quadrupolar nuclei, a 1 M solution of a salt in water should be used). Put the relevant
tuning rod into the probe. Connect the correct coil in the correct pair of connectors
on top of the probe body. Refer to the probe installation manual for details on setting
up the wideline probe.

2. Place a sealed sample of 2% D

O in the probe and put the probe into the magnet.

2

Connect body air, VT gas and the “Normal” connector on the magnet leg to the
probe. No filters are necessary . Make sure that the 30–60 MHz 1/4-wa velength cable
is on the magnet leg.

3. Enter setup('H2','d2o') dm='n' su. Tune the probe as described in the

probe installation manual.

4. Now , instea d of the observe channel, connect the lock channel to the probe. Lock the
spectrometer in the usual way.

The spectrometer can now be shimmed using acqi, but there is no point trying to
obtain a resolution that is markedly better than the lines to be observed, so that only
the gradients X, Y, Z1 Coarse, and Z2 Coarse need be optimized.

O (for most other

2

5. Make sure that the lock and spinner are deactivated by selecting LOCK OFF, SPIN
OFF, SPIN=0 and setting lockpower=0.

6. Replace the lock connection with the observe channel. Check the tuning and then
make sure that the probe is connected to the “Normal” position on the preamplifier.

7. If not already done, reset the solids cabinet, and make sure the broadband 1 kW
amplifier is on and that no interlocks are activated. Set the switch panel so that the
LOWBAND is on HI POWER.

8. Set sw=1E5 pw=2 np=1E4 d1=4 nt=1. Set tpwr to the standard value for the
system. If no value has been determined previously, set tpwr=55.

9. Set gain='n' and acquire a spectrum. Phase correct the res ult and ensure that the
spectrometer is working correctly. If necessary, use movetof to place the D

O

2

signal exactly on resonance.

10. Check these adjustments by reacquiring a spectrum.

11. Array pw to determine the 180

° or 360° pulse width. Set gain='y' (because

arrayed experiments cannot use Autogain) and acquire the data. Determine the 90
pulse width to 25 ns resolution.

12. Set pw and pw90 to the 90° pulse width value.
This completes the calibration procedure.

°

53

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

3.5 Standard Wideline Samples

13. Replace the D2O sample with the malonic acid–d4 sample and tune the probe.

14. Enter ssecho to con vert the s2pul parameter set to one suitable for the SSECHO
pulse sequence. Set tau1=20 tau2=15 nt=16.

15. Set gain='n' and enter go to acquire data.

16. Enter df to display the FID. Use the phase button and the mouse to maximize the
real (cyan) channel. Set lsfid=0. Put a single cursor on the echo maximum and
enter tmove. Transform the FID.

17. Phase correct the spectrum using rp only (set lp=0). Select two cursors and set
each on top of a horn of the powder pattern. Enter split to move the right cursor
to half way between the two horns. Entering movetof then sets the observe
transmitter to this position.

18. Reacquire data, this time with d1=10.

19. Enter df to isplay the FID. Maximize the real channel as in step 16 and put a single
cursor at the echo maximum, putting it between data points if necessary.

This FID can either be transformed or data reacquired starting from the cursor
position. If the FID is to be transformed, then enter tmove wft. Phase correct the
spectrum as before. If new data is to be acquired starting at the cursor position, enter
tshift followed by go or ga.

Other spectra can now be acquired using these parameters.

Obtaining a Wideline Spectrum of 23Na

Sodium does n ot normally have a parameter set in stdpar, so it is necessary to call up
some standard set and modify it. The easiest way to do this is shown in step 1 below.

1. Enter setup('H2','d2o') tn='Na23' dm='n' su.

2. Set up the probe with the correct coil and tuning rod (if any) and put in a sealed
sample of NaCl (1 M in H

O). Tune the probe as described in the probe installation

2

manual.

3. Follow step 5 through step 12 in “Obtaining a Wideline Spectrum of Deuterium,”

page 53.

4. Remove the sealed sample of NaCl (1 M in H

O) and replace it with the sample to

2

solid sodium nitrate.

5. Tune the probe and enter ssecho to convert to the QUADECHO sequence and
acquire 16 transients using a d1 of 1 second.

6. Process the spectrum the same as fo r deuterium, except that the center of the po wder
pattern is the center of the highest line.

Hints for Performing Wideline Experiments

If a powder pat tern sho ws more than 3- 4% asymmetry in the height of the horns, check that
the sample is centered in the coil. If this is the case, check the tuning of the probe. If neither
results in a significant improvement, shift the transmitter position 1000 Hz towards one
horn. Finally, recalibrate the 90

° pulse with a solution sample, then retune the probe to the

same reflected power level.

can be very long in solids. It may be necessary to set d1 to values of the order of

• T

1

100 seconds in some cases.

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

54

Chapter 3. Wideline Solids Module Operation

• Remember that for solid samples of quadrupolar nuclei, the 90° pulse usually cannot

be determined from a pw array.

3.6 Data Processing

Most data processing needs of wideline spectra are the same as that f or other spectra. Ther e
are, however, several specialized applications, for which software is provided. Since most
wideline spectra are collected in a spin-echo mode, it can be extremely important to start
acquisition, or at least Fourier transformation, on top of the echo. The FID display program
provides a point-by-point (if dotflag='y'), two-color display of the r eal and imaginary
channels of the FID in order to provide the best possible examination of the details of the
FID. One or two time cursors can also be displayed and are not constrained to fall on top
of individual data points but may be used to interpolate as well (for example, to estimate
the time of the echo). A left shift of the FID may be used to shift the FID until the echo
occurs at the first point of the FID.

Normally, the echo top is well enough defined so that left shifting removes all distortion.
However, this is not always the case, especially with very short T
fractionally left shifting has been provided as follows:

lsfid='n' phfid='n'
ft
ft('inverse',
jexp

n

scalesw=1.0/
df
wft

n

,expn)

n

echoes. A means of

2

In this example, n in the ft command is a interpolation factor (power of 2); expn is an

n

experiment number for the interpolated FID; df interpolates the FID by a factor of

n

the echo top may be picked more accurately; scalesw=1.0/

will correct sw.

and

It is also common to collect wideline spectra with the transmitter placed in the exact center
of the resonance. Software is provided to allow “phasing the FID” to place as much as
possible of the FID in the real channel. This operation means that the frequency­independent phase shift of the spectrum is as close to zero as possible, which is beneficial
since frequency-domain phasing of wideline spectra can be difficult at best. In addition,
spectral symmetry can be forced by software that sets the imaginary channel of the FID to
zero.

55

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

Chapter 4.

Sections in this chapter:

• 4.1 “Introduction to Multip ul se Exper im ents,” this page

• 4.2 “CRAMPS/Multipulse Module Hardware,” page 57

• 4.3 “Multipulse Experiments and User Libra ry,” page 60

• 4.4 “Multipulse Tune-Up Procedure (FLIPFLOP) ,” page 60

• 4.5 “

• 4.6 “How to Obtain Good CRAMPS Spectra,” page 65

• 4.7 “Quadrature 1H CRAMPS,” page 66

• 4.8 “Fast MAS Assisted with a Multiple-Pulse Cycle (WaHuHaHS),” page 67

• 4.9 “FL IPFLOP - Pulse Width and Phase Transient Calibration,” page 68

• 4.10 “ BR2 4 and CYLBR24 - Multiple Pulse Line Narrowing (24-pulse cycle),” page

• 4.11 “ MREV8 and CYLMREV - Multiple Pulse Line Narrowing (8-pulse cycle),”

• 4.12 “WaHuHa and WaHuHaHS - MP-Assisted High-Speed Spinning (4-pulse

CRAMPS/Multipulse Module Operation

1

H CRAMPS Experiment (B R24 or MREV8),” page 6 4

69

page 70

cycle),” page 71

4.1 Introduction to Multipulse Experiments

Multipulse describes a class of experiments that require the interleaving pulses with the
acquisition of the data points of the FID. Combined Rotation and Multipulse, CRAMPS,
is the most common
resolution MAS
BR24 multiple-pulse cycle. A BR24 multiple-pulse cycle applies 24
dwell time between the acquisition of complex data points. Multiple-pulse cycles such as
BR24 removes strong
materials. Slow-spinning MAS averages the
widths of 0.25 ppm to 3 ppm.

Hardware for the
Module or by a Full Solids setup and is described in this chapter alo ng with setup
procedures.

Multiple-pulse cycles are often employed without interleaved data acquisition in many
solids sequences for the purpose of decoupling and recoupling, or during the evolution
period in two-dimensional experiments. This chapter describes the procedures used to
adjust the pulsewidth and phase transient for CRAMPS and other multiple-pulse cycle
experiments. The tune-up sequences described in section 4.4 “Multipulse Tune-Up

Procedure (FLIPFLOP),” page 60.

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

1

H high-resolution experiment. CRAMPS is used to obtain high-

1

H spectra of organic materials. The CRAMPS pulse sequence uses the

1H-1

H dipolar interactions that broaden the spectra of organic

1

H CRAMPS experiment is provided by the 1H CRAMPS/Multipulse

1

H chemical shift tensor to yield typical line

1

H 90o pulses in the

56

Chapter 4. CRAMPS/Multipulse Module Operation

4.2 CRAMPS/Multipulse Module Hardware

Multipulse capability is available with all
UNITY and VXR-S spectrometers require an additional Sync Module to improve pulse­timing stability. The main CRAMPS/multipulse module hardware is the motor control box,
1-kW amplifier , sync module (UNITY and VXR-S systems only), an d the CRAMPS probe.

1

H CRAMPS experiment requires the following:

The

1H/19

•

F 1-kW amplifier (see 2.1 “CP/MAS Solids Modules,” page 16)

• Fast ADC (2 MHz or 5 MHz)

• Solids high-power preamplifier

• Suitable MAS probe with pneumatics hardware
See 2.2 “Rotor Characteristics and Composition,” page 20 to 2.4 “Spinning the

Sample,” page 22 for information abou t MAS spinni ng.

1H/19

F 1-kW Amplifier

1H/19

F 1-kW amplifiers suitable for CRAMPS are described in section 2.1 “CP/MAS

Solids Modules,” page 16. The CRAMPS experiment generally requires more than 100

Watts of power. A very small-diameter rotor will facilitate running the experiments with a
100 Watt CP/MAS amplifier in some cases.

UNITY

INOVA and UNITYplus spectrometers.

Amplifier Tuning

The CPI amplifier is tuned to either 1H or 19F. At 600 MHz only 1H tuning is possible.

INPUT TUNING uses the 20-turn pot at the f ront of the amplifier ch assis. The ou tput tuning

uses the external Motor Control Box. A 3-position selector switch is used to choose

LOAD and STANDBY (AUX). The COARSE and FINE toggles are momentary contact and

can be pushed in two directions (designated

IN and OUT) to adjust either the TUNE or LOAD

TUNE,

depending upon the selection set on the 3-position selector switch.

1

A CMA amplifier is tuned to either
pots at the bottom-front of the amplif ier chassis.

H or 19F. INPUT TUNE and INPUT MATCH are 20 turn

OUTPUT TUNE and OUTPUT MATCH are

digital knobs at the center-front of the chassis.

Tune the Amplifier

1. Connect the amplifier output (the cable to the connection XMTR J5313 on the
preamplifier) through at least a 30 db attenuator to an oscilloscope or a power meter.
The attenuator must handle 50 Watts or more.

2. Do one of the following depending upon the type of amplifier:

• CMA amplifier only
Select the mode as either

“Amplifier and Receiver Blanking,” page 58).

• CMA or CPI amplifier

a. Set a single repeating pulse of pw = 300

19

F. Tune the input tuning pot(s) for maximum power or voltage.

or

b. Iteratively adjust the output tuning ( tune and "load" or "match") for maximum

power or voltage.

GATE ACTIVE or CLASS C as required (see

µs with a d1=30 µs for either

1

H

57

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

4.2 CRAMPS/Multipulse Module Hardware

c. After tuning at lower power, fine tune at the maximum pow e r that will be

used in order to obtain the maximum linearity of the CPI or the CMA.

d. Record the values for future reference.

Overdrive Mode

The CPI amplifier contains an OVERDRIVE RESET button on the front panel. An overdrive
state is indicated by the lighted red word on the relay panel at the top of the solids bay. Press
to reset when the word is lighted. The CMA amplifier contains a

TRIP RST button and an

overdriv e state is indicated by a red light on the front o f the ch assis . I n overdrive mode the
amplifier is shut down. An overdrive fault is caused by excessive power or an arc in the
probe, and sometimes by pulsing into a mismatched cable. The overdrive usually must be
reset when the acquisition computer is restarted.

Amplifier and Receiver Blanking

The BR24 pulse sequence for CRAMPS, makes use of amplifier blanking to remove
amplifier noise during the acquisition of data points between the pulses. Set the parameter
ampmode = p or d for pulsed mode. The p arameter ampmode is also set correctly if the
parameter is not present. The newer CMA amplifiers should be run with the toggle in the

GATE ACTIVE (pulsed) position. Older CPI amplifiers are automatically set to pulsed mode

using the value of the ampmode parameter.
In pulsed mode the CPI and CMA amplifiers are turned on at the beginning of the period

rof1 before the pulse. They are ready for full RF output after rof1=1.5 to 2.0
minimum value of rof1=1.5
a period rof2=0.2 to 0.5
down” over a period of about 2.0-3.0

µs is used for CRAMPS. The amplifiers are turned off after

µs after the pulse. For

1

H CRAMPS the noise and RF “ring

µs before detection of a data point is possible. During

µs. The

this period the T/R switch (if present - see Solids Preamplifiers below) immediately gates
to receive mode and th en after a delay a trigger is sent to turn the receiver on. When using
the fast ADC the receiver then turns on within about 1.0

µs

The delay between triggering the T/R switch and the receiver is set by a hardware
adjustment on the magnet leg. The d ef ault value is about 2.0 microseconds for a highban d
nucleus and about 8.0 microseconds for a lowband nucleus. The purpose is to protect the
receiver (outside of pulse-sequence control) from pulse ring down that will “certainly” be
present. If one collects a data point before the receiver turns on by setting tau too short in
BR24 or FLIPFOP , the result will be a null signal. In this case lengthen tau. The hardware
delay is accessible to users and can be made shorter if desired to allow smaller values of
tau.

Optionally, a CMA amplifier may be set in CLASS C (nonlinear) mode. In this case the RF
pulse of the 50-Watt driver amplifier turns the CMA on and off. Blanking instructions of
the pulse sequence are ignored. Set ampmode='c' to operate the 50 watt driver in
continuous mode. CLASS C mode provides a slightly shorter unblanking time (rof1) but
RF output in CLASS C mode is not linear. It will be necessary to retune and recalibrate the
parameters tpwr and tpwrfor tpwrm when using CLASS C mode.

FAST ADC (2 MHz or 5 MHz)

The CRAMPS experiment requires an optional fast ADC, which may be either 2 MHz or 5
MHz. This device sits in the acquisition card cage and is connected to the receiv er ports WB
CH A and WB CH B (J246 and J247) with a pair of BNC cables. These ports provide the
real and imaginary FID signals and b ypass the analog filters. The u nfiltered FID signal from

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

58

Chapter 4. CRAMPS/Multipulse Module Operation

the receiver and the fast ADC have a sufficiently short turn-on time for detection between
the pulses of BR24. Note that the value of sw in BR24 is set to 2 MHz to select the fast
ADC but the true dwell time is longer since the pulse sequence is responsible for turning
on and off the receiver and digitizer.

Note that the dwell time of the 500 kHz ADC of
but the turn-on time is not. Optionally, one can bypass the fast ADC with a custom cable
(not provided) that connects the unfiltered receiver outputs to the 500 kHz ADC. A special
BR24 pulse sequence can be written that compensates for the slower turn-on time of the
500 kHz ADC. This configuration can be set up by users, but it is not supported.

Solids Preamplifiers

For 300 MHz and 400 MHz systems an optional special high-power, 0-400 MHz
preamplifier module is available. This preamplifier has a passiv e T/R switch (in contrast to
the active T/R switch of the standard preamplifier module) and additional heat sinking on
the diodes to withstand a greater RF duty cycle. This preamplifier may also be used for lo w
band solids observe. This preamplifier can be used in-line during
labeled

Newer systems and all systems 500 MHz and ab ov e use a
module is supplied with an active T/R switch. The preamplifier module has a built-in l/4
cable and a high-pass filter (needed for CP/MAS) and can be used in-line during
decoupling. The appearance of this preamplifier is indistinguishable from standard
module. Check the part number s and instrumen t documentation if there is any doubt about
an existing preamp. Set rof2=0.5

High Power - 990888. Set rof2 = 0.2 µs.

µs.

UNITY

INOVA is sufficiently fast for BR24

1

H decoupling and is

1H/19

F high-power preamplifier

1H/19

F

Other preamplifiers are not suitable for CRAMPS and cannot be in line during CP/MAS
decoupling. Ring down of these preamps may be too long or the diodes may n ot withstand
the RF duty cycle.

MAS Probes for CRAMPS

Any CP/MAS probe with a 1H-decoupler channel can be used for 1H CRAMPS. The
quality of the result depends upon the minimum pulse width that can be obtained and the
inherent resolution of the sample. Highly crystalline materials have linewidths of less than

o

µs 90

0.5 ppm. T o achiev e these line widths one should use a 1.5
polymers may have minimum line widths of 3 ppm. A 90

o

pulse or less. Amorphous

pulse of 3.0 to 4.0 microseconds

may provide all the narrowing that is needed to obtain a result. Consult the probe

o

specification to determine the available 90

pulse.

Varian provides a 5 mm narrow-body single-tuned CRAMPS probe for 300 MHz and 400

19

MHz magnets, which can be tuned from

F to 1H. This probe uses a body and a 5 m m rotor
similar to the Auto-MAS CP/MAS probes. The zirconia stator of the Auto-MAS probe
uniquely provides very low 1H background. For widebore magnets a 5 mm Chemagnetics
CRAMPS probe is available. In addition, any Auto-MAS CP/MAS probe or widebody
Chemagnetics CP/MAS probe with a rotor size of 5 mm or less can b e used f or CRAMPS.

Sync Module (UNITY, VXR- S only)

The Sync Module, located on the wideline receiver, provides a buffered 500 kHz signal
derived from the mas ter oscillator. Its output is connected to the
the output board. A pulse sequence can delay until the next clock edge by using the pulse
sequence element xgate(1.0). Clocking the beginning of the pulse sequence on 500
kHz output improves timing stability of the pulses for UNITY and VXR-S spectrometers.

EXT TIMEBASE input on

59

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

4.3 Multipulse Experiments and User Library

4.3 Multipulse Experiments and User Library

The macros for some of the multipulse NMR sequences are located in maclib. The
macros for other multipulse NMR sequences are located in the user library userlib.

User Library—Terms and Conditions

Material submitted to the user library is distributed by Varian as a service to its
users. All rights to the material submitted are retained by the submitter, unless
explicitly surrendered in the accompanying README document.

You may not redistribute anything in the user library in any form to anyone outside
of your own organization, without the express permission of the submitter.

Neither V arian, Inc. nor the submitter makes any warranty or representation of any
kind, express or implied, with respect the material found in the user library.

This material is distributed “as is,” and you as sume the entire ris k as to the qu ality,
reliability, and performance of any software you choose to use.

In no event shall Varian, Inc. be liable for any consequential, special, incidental,
direct, or indirect damages of any kind aris ing out of the use o f software in th e user
library.

Use of any material in the user library shall constitute acceptance of these terms and
conditions.

4.4 Multipulse T une-Up Procedure (FLIPFLOP)

The pulse sequence flipflop.c is used to perform both the XX (FLIPFLIP) or X-X
(FLIPFLOP) tune-up experi ments.

To tune up for CRAMPS or other multiple-pulse sequences accurate measurement the
proton 90
procedure that follows uses a narrow-line liquids sample with repeating X pulses and
interleaved acquisition.

Prepare the Sample

o

pulse and minimization of the effects of RF inhomogeneity is required. The

1. Fill a small glass bulb with a single-line protonated solvent such as b enzene, dioxane
or water.

An organic solvent is recommended since its affect on probe tuning is similar to that
of an organic solid. Add a bit of the relaxation agent CrAcAc (not provided) to the
organic solvent to shorten T

2. Center the bulb in the coil.
Alternatively , a small solids sample of RTV (silicon rubber caulk from the hardware

store) will provide a
during these measurements.

1

H linewidth sufficient for tuning. Spin the RTV at about 2 kHz

.

1

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

60

Chapter 4. CRAMPS/Multipulse Module Operation

Configure the Spectrometer

1. Connect the preamplifier and cable that are used for 1H detection to the 1H port of
the probe to be used.

1

If this is a tune-up for

H decoupling instead of CRAMPS, the preamplifier must

remain in line during the decoupling experiment.

2. The presence or absence of the preamplifier in the circuit will make a significant
difference in pulse widths. A Solids preamplifier that is suitable for CRAMPS can
also remain in line during decoupling. Do not use the standard T/R switch in a
decoupling circuit unless you know it has been specified for solids.

Adjust the Homogeneity and Determine an Approximate 90o
Pulse

1. Collect a single pulse 1H spectrum of the sample.

2. Shim for a minimum line width (<50 Hz).

3. Roughly measure the 90
It is convenient but not mandatory to use Z0 to place the signal on resonance with

tof=0.0. Be sure the receiv er gain is lo w s o as to a v oid o v erload (gain<20) and
d1 is set to insure full recovery of the signal.

o

pulse and place the signal on resonance.

Calibrate the Exact 90o Pulse Width (FLIPFLIP or XX)

This procedure is accomplished by retuning the probe or amplifier while observing
a repeating cycle of alternating X and -X pulses. The procedures for tune-up are as
follows:

1. Enter the macro flipflop.

2. Set the following permeates according to the system in use:

UNITY

Parameter

d1 1.0 sec 1.0 sec Longer for samples with no relaxation agent
rof1 1.5 µsec 1.5 µsec
rof2 0.2 µsec 0.2 µsec
pw <1.5µsec <1.5µsec 1.5 usec is optimal for CRAMPS
tau 7.0 µsec 7.0 µsec add pulse width in excess of 1.5 µsec the value

phase1 00
phase2 00
phfid 00
nt 11

trig ‘n’ ‘y’ Rotor sync. module is re quired to se t

INOVA or

UNITYplus

UNITY or
VXR-S

Comments

base value, e.g. is pw =2.5 then tau = 8.0 usec

trig=’y’

61

3. Acquire a FID and enter df to display both the real and imaginary points.
Obtain the imaginary trace with the imaginary menu button. Adjust the phase to

minimize the imaginary channel. If this is not possible, check to be sure the FID is
on resonance.

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

4.4 Multipulse Tune-Up Procedure (FLIPFLOP)

• Optionally
a. Type phaser=phfid, phfid='n'

b. Reacquire the spectrum.

This will adjust the pulse phase to place the signal in one of the two ADC
channels. Otherwise, it usually sufficient to observe a phased display. The
real channel should appear similar to Figure 17. or Figure 18.

Figure 17. Real Channel FID Pattern

Figure 18. FLIPFLIP FID at Exact 90° Pulse

4. Type gf and then acqi.

5. Press the FID button and then press again to select the FID display.

6. Press IPA and adjust the tpwrf slider to achieve a display similar to Figure 18.
The ideal signal pattern (1.0,0.0,-1.0,0.0)N results from a 90

o

pulse. The bulge
among the first few zero-points and the decay are due to RF inhomogeneity. A
distribution of pw90 values interferes to cause the pattern of Figure 18.

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62

Chapter 4. CRAMPS/Multipulse Module Operation

The RF homogeneity can be enhanced by reducing the sample size and by using care
to center the sample in the coil. Data similar to Figure 18 is suitable for most
CRAMPS experiments. Probes with a strong
modules of Chemagnetics CP/MAS probes) will show an initial offset of all the
points, that decays to zero. Probe backgro und is subtracted by the BR24 exper iment
and can usually be ignored.

Remove phase trans ien t (FLIPFLOP or X-X)

1. Type phase2=2.
This changes the experiment to FLIPLOP or X-X.

2. Type gf and then acqi.
The result should be a parallel set of points similar to Figure 19 or Figure 20. The

transmitter must be on resonance to correctly run X-X.

3. Adjust the system tuning (see “System Tuning,” page 63) to remove the cur vature of

Figure 19. and obtain a result similar to Figure 20.

1

H background (typically the Vespel,

Figure 19. FLIPFLOP “Tram Tracks”

Figure 20. FLIPFLOP Desired FID

System Tuning

The ideal signal pattern is (1.0,0.0)N. Curvature similar to Figure 19 results from phase
transient or phase “glitch”. Phase transient is a small shift, f(t) in phase during the rise and
fall times of the pulse. Asymmetric phase transient (

φ(τ) during the fall time) causes a net phase shift with each pulse of X-X. This shift causes

­a frequency offset of the entire pattern. The same effect will occur in the CRAMPS
experiment.

Phase transient can be removed or balanced by adjusting tuning of the duplex circuit
containing probe, amplifier , quarter-wa ve cable and preamplifier . A small adjustment of the
probe tuning capacitor is often quite ef fecti v e. I n this case record the v alue of the r eflected

φ(τ) during the rise time is not equal to

63

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

4.51H CRAMPS Experiment (BR24 or MREV8)

output on the tune-interface or note the frequency of the minimum reflected output with
qtune. Return to this value when tuning the sample. Phase transient can also be removed
more-or-less permanently by carefully cho osing the precise length of the cable between the
preamplifier and the probe, or if accessible, the l/4 cable on the preamp. In this case,
continue to use the same cables for future experiments. Theoretically, tuning of the CMA
or CPI amplifier can also affect phase transient. In practice amplifier tuning does not
usually remove phase transient.

4.51H CRAMPS Experiment (BR24 or MREV8)

BR24 is the standard experiment used to obtain 1H CRAMPS data. MREV8 provi des
slightly less narrowing eff i cienc y b ut can accommodate a larger chemical range.

1. Use the tune-up sample, with a calibrated parameter set for FLIPFLOP

2. Type br24 or mrev8.

3. Set pw to the calibrated pulse width

4. Set tpwr and tpwrf to the calibrated power levels.

5. Type tau = 3.5

6. Verify th e following:
rof1 = 1.5

7. Set the following parameters:

p1=pw (BR24 only).
d1 is correct (d1=1.0 with a relaxation agent)

Set trig='n'(trig='y' for UNITY and VXR-S with a Sync Module)

8. Array tof in 1 kHz steps form -1e4 to +1e4.

9. Type ga.
The resulting display should show a single resonance that moves with tof.

Measure the frequency shift of the resonance with each chang e in of fs et. This v alue
divided by 1000 is the experimental multiple-pulse scale factor, S. S will probably
be offset dependent. Choos e tof wit h the greatest narrowing (a value of
tof=-2000 to -5000 is often obtained). This will be the optimum tof for future
experiments. Note the shift of the spectrum when tof is on resonance. This shift
should be zero. If the offset is large (>500 Hz) , it will be necessary to repeat step 3
and step 4, on page 62.

Optional:

a. Fine adjust the phase transient using BR24 or MREV8 to obtain a zero of fset.
b. Run a set of repeating scans in acqi mode and tune phase transient to place

the signal with tof=0 at zero frequency.
Probe heating may cause a time dependent line shift that results from a change

in phase transient due to a change in probe tuning. If this is a problem increase
the VT air (Chemagnetics probes) and the body air and use steady-state scans
if necessary to begin the run at equilibrium.

µs plus any excess pw greater than 1.5 µs.

µs and rof2 = 0.2 µs.

10. Record the tuning values for Qtune or the tun e interface for future use in tuning the
probe with the sample.

11. Insert a sample of solid adipic acid or glycine and retune to the previous values.

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Chapter 4. CRAMPS/Multipulse Module Operation

12. Set the spin rate at < 2 kHz.

13. Set d1=5 for glycine and d1=60 for adipic acid.

14. Type nt=2 ga
The result for adipic acid should be similar to Figure 21.

15. Scale the spectrum.

a. Place two cursors on the two upfield lines of adipic acid or glycine.
b. Type scalesw=sfrq/delta.

16. Reference the spectrum.

a. Place a cursor on the upfield of the two lines
b. Type rl(sfrq*2.0/scalesw) to reference this line at 2.0 ppm.
c. The chemical shift scale and reference are now correct and an additional line

should be present at 13 to 14 ppm.

17. Run the experimental sample with the same data set and tuning.

4.6 How to Obtain Good CRAMPS Spectra

MREV8 and BR24 pulse sequences must be used with slow spinning so that the length of
a rotor cycle, tr, greater than one multiple-pulse cycle, tauc. Interference between these

1

two cycles will negate the narro wing ef fects. Typical spinning speeds for

H CRAMPS are

less than 2 kHz, and at these speeds the multiple-pulse cycle does all the narrowing of

1H-1

H dipolar interactions.

65

ppm (sc)24681012141618

Figure 21. Adipic Acid Spectrum

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

4.7 Quadrature 1H CRAMPS

The transmitter is typically set upfield (tof=-2000 to -5000 Hz) from the spectrum of
interest and line narrowing is usually best at these frequencies. MREV8 and BR24 spectra
also always hav e a quadrat ure image and a zero-freq uency signal (the "pedestal") and it is
necessary to set the transmitter off resonance to avoid overlap with these signals. The
section below (“Quadrature 1H CRAMPS,” page 66) describes how to a v oid imag es and a

1

pedestal. A pedestal can also be caused by
experiences a flip angle much less than 90

H background in the probe. Background

o

and does not precess. The result is a

zero-frequency signal .
Multipulse sequences deliver substantial RF to the probe. Probe heating is a possibility,

especially if the sample is lossy, and heating can cause a probe tuning change and a
degradation of the CRAMPS spectrum. Use VT air when available and consider using
steady-state scans to establish a steady-state tuning condition in the probe. If you are
collecting many scans, tune with a duty cycle about the same as that of the spectrum
(similar d1, tau and ss).

1

The power for obtaining minimum
(unless otherwise mentioned) is usually a value that can be sustained for about 50 ms with
a 100% duty cycle (i.e.

1

H decoupling). The duty cycle of a CRAMPS sequence is about

H 90o pulse width for a particular CP/MAS probe

30% to 50%. At this power level it is safe to run a CRAMPS experiment with the same total­time and longer acquisition times or slightly shorter pulses can be considered. There is no
specific rule here except that one should consult the manufacturer before exceeding
specifications in the case a probe is under warranty. Use as short a 90

o

pulse that you feel

is safe for a given probe.
The quality of a CRAMPS spectrum is impro ved by shortening the interpu lse spacing, tau.

The lower limit for tau is determined by the time required to collect the data point during
one of the 2*tau periods of the pulse sequence. The recommended tau = 3.5
provides a 5.5

µs window to collect a data point when pw=1.5 µs. Smaller values will

result in a null signal (see “Amplifier and Receiver Blanking,” page 58). One can shorten
tau can be shortening by changing the hardware adjustment that delays receiver turn on.
The result will be a signal that includes some probe ring down, which will appear as a larger
pedestal. The CRAMPS sequences also subtract ring down with a phas e cycle of 2 scans so
one can afford a certain amount of ring down in ones CRAMPS data points, as long as it
does not saturate the ADC.

4.7 Quadrature 1H CRAMPS

The pulse sequences CYLBR24 and CYLMREV provide quadrature detection and
suppress the pedestal and the image. Fo r MREV8 and BR24 an of f-resonance signal created

o

by a 90
pulses rotates the magnetization about an axis tilted relative to Z. The real and imaginary
components projected on the XY plane are not equal and the result in the spectrum is a
quadrature image. In addition, if magnetization is not completely tilted to the plane of
multipulse precession by the preparation pulse, the remaining component of the
magnetization will not precess and cause a pedestal.

The two quadrature multipulse experiments ha ve 4 -scan phase c ycles. F or each o f the four
scans the phase and flip angle of the preparation pulse are set to rotate the magnetization to
each of the four 90
phases and flip angles. In these sequences the flip angle and small-angle phase are varied

pulse does not precess in the XY plane. Instead the combination o f precession and

o

positions in the plane of precession. Table 8 and Table 9 show these

µs

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Chapter 4. CRAMPS/Multipulse Module Operation

scan to scan. When set properly, a four scan phase cycle should remove both the image and
the pedestal and it should be possible to set the transmitter in the center of the spectrum.

Table 8. Multiacquisition Quadrature Corrections for MREV8

Acquisition M(0) Preparation Pulse (degrees)

1 (0,1,0) 90
21/√2(1.0,–1) 135
3 (0,–1,0) 90
4 1/√2(–1,0,1) 45

0

270
180
90

Table 9. Multiacquisition Quadrature Corrections for BR24

Acquisition M(0) Prepara tio n Pu lse (degrees)

11/√2(1,1,0) 90
21/√6(1.–1,–2) 145
31/ √2(–1,–1,0) 90
41/√6(–1,1,2) 35

315

220
135
45

There are no drawbacks to using the quadrature sequences instead of BR24 and MREV.

4.8 Fast MAS Assisted with a Multiple-Pulse Cycle
(WaHuHaHS)

High MAS spin rates (>15 kHz) also average 1H-1H dipolar interactions and are an
alternative to
approaching 30 kHz provide line narrowing that can compare with
advantage of fast s pinning is greater sensiti vity. Fast-spinning spectra can be acq uired with
analog filters fb set just greater than the spectral width for a large sensitivity improvement.
It is in fact useful to set sw equal to the spin rate to eliminate any sidebands. In contrast
multipulse methods must use open analog filters to avoid pulse ring-down, and folded noise
from the full receiver bandwidth (2-5 MHz) lowers the signal to noise.

1

H CRAMPS. Used with direct polarization alone, spinning speeds

1

H CRAMPS. An

67

One multipulse sequence, WaHuHaHS, can be used with fast MAS spinning. W aHuHaHS
is a semi-windowless version of the original multipulse sequence, WaHuHa. Both
sequences have a four-pulse cycle. In WaHuHaHS two of the interpulse de lays are set to
zero and the total cycle time, tauc, is short enough to be used with high speed spinning. The
result is often an improvement over high-speed spinning alone or slow spinning 1H
CRAMPS.

WaHuHaHS requires the same multi ple-p ulse set-up procedure described above for
MREV8 and BR24.

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

4.9 FLIPFLOP - Pulse Width and Phase Transient Calibration

4.9 FLIPFLOP - Pulse Width and Phase Transient
Calibration

The flipflop.c pulse sequence (Figure 22) is the standard sequence for multiple-pulse tune
up. It is applicable for UNITYplus and

UNITY

INOVA as well as UNITY and VXR-S with
a Sync Module. It is used for measurement of the pulse width and removal of phase
transient.

[phase1] [phase2]

d1

pw

'np'/4 times

acq

dtau rof1rof2

tau tau

pw

acq

dtau rof1rof2

Figure 22. Pulse Sequence for flipflop.c

Macro

The macro flipflop calls the sequence and a parameter set.

Parameters

pw is the 90o pulse length, in microseconds.
phase1 is the phase of the first 90-degree pulse, and is set to 0 (x).
phase2 is the phase of the second 90 d egree pulse. It is set t o 0 (x) for FLIPFLIP and 2 (-x)

for FLIPFLOP.

trig='y' for UNITY and VXR-S with a Sync Module. Otherwise trig='n'.
np is the number points and np=128 or 256.
tau is interpulse delay, in microseconds, including pw. The minimum tau is about 7.0

when pw=1.5

µs. See rof1 and rof2.

rof1 is the amplifier unblanking time before each pulse. The recei ve r is also immediately
blanked and a T/R switch if present is placed in transmit mode. Set rof1=1.5 µs.

rof2 is the receiver unblanking time after each pulse. A T/R switch is placed in receive

1

mode immediately. For

H the receiver comes on after about 2.0 µs. For lowband nuclei

the receiver is set to come on after 8.0 ms. these two times are controlled by hardware
adjustment in the magnet leg. Set rof2=0.2

rof2=0.5

µs for a Solids

1H/19

F preamp.

µs for a High-Power preamp. Set

µs

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Chapter 4. CRAMPS/Multipulse Module Operation

4.10 BR24 and CYLBR24 - Multiple Pulse Line Narrowing
(24-pulse cycle)

Br24 (Figure 23) is the usual sequence used for 1H CRAMPS. CYLBR24 is a modif ication
that allows quadrature detection with the transmitter in the center of the spectrum. The
sequences are applicable for UNITYplus an d
with a Sync Module.

UNITY

INOVA as well as UNITY and VXR-S

d1

prep

acq

'np'/2 times

pw

tau

2*tau

Figure 23. BR24 Pulse Sequence

Macros

The macro br24 converts a S2PUL or FLIPFLOP data set for BR24. cylbr24 converts
a data set for quadrature BR24. All relevant parameters are preserved if the initial data set
is FLIPFLOP, BR24, CYLBR24, MREV8 or CYLMREV.

Parameters

pw is the 90o degree pulse-length, in microseconds.
p1 is the preparation pulse, in microseconds, whose phase is controlled by the parameter

phase1. To minimize the “pedestal” p1 should be set to the 90
phase1=135.

o

flip angle and

69

tau is the interpulse delay, in microseconds, including pw. The BR24 cycle is 36*tau
long and is repeated np/2 times to build up a FID.

trig='y' for UNITY and VXR-S with a Sync Module. Otherwise trig='n'.
tauc is the cycle time, in microseconds and is the actual dwell time for the FID. tauc is

not changed and is for information only.
mp_at is the sum of all cycles, in microseconds, and is the true acquisition time. mp_at

is not changed and is for information only.
sw=2e6 turns on the fast ADC without analog f ilters. sw does not determine the dwell time

(see tauc).

scalesw is a scale factor that converts sw=2e6 to the correctly scaled spectral width.
scalesw=(1.0/tauc*sw)*S where S is the multiple-pulse scale factor for Br24

(0.385 for ideal pulses).
rof1 and rof2 (see 4.9 “FLIPFLOP - Pulse Width and Phase Transient Calibration,”

page 68)

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

4.11 MREV8 and CYLMREV - Multiple Pulse Line Narrowing (8-pulse cycle)

4.11 MREV8 and CYLMREV - Multiple Pulse Line Narrowing
(8-pulse cycle)

MREV8 (Figure 24) is a sequence used for 1H CRAMPS. CYLMREV is a modification
that allows quadrature detection with the transmitter in the center of the spectrum. The
sequences are applicable for UNITYplus an d
with a Sync Module.

UNITY

INOVA as well as UNITY and VXR-S

acqprep

0321

d1

pw

03 2

'np'/2 times

1

tau 2*tau

Figure 24. MREV8 Pulse Sequence

Macros

The macro mrev8 con verts a S2PUL or FLI PFLOP data set for BR2 4. c ylmre v converts a
data set for quadrature MREV8. All relevant parameters are preserved if the initial data set
is FLIPFLOP, BR24, CYLBR24, MREV8 or CYLMREV.

Parameters

pw is the 90o degree pulse-length, in microseconds.
tau is the interpulse delay, in microseconds, including pw. The MREV8 cycle is 12*tau

long and is repeated np/2 times to build up a FID.
trig='y' for UNITY and VXR-S with a Sync Module. Otherwise trig='n'.
tauc is the cycle time, in microseconds and is the actual dwell time for the FID. tauc is not

changed and is for information only.
mp_at is the sum of all cycles, in microseconds, and is the true acquisition time. mp_at

is not changed and is for information only.
sw=2e6 turns on the fast ADC without analog f ilters. sw does not determine the dwell time

(see tauc).

scalesw is a scale factor that converts sw=2e6 to the correctly scaled spectral width.
scalesw=(1.0/tauc*sw)*S where S is the multiple-pulse scale factor for MREV8

(0.471 for ideal pulses).
rof1 and rof2 (see 4.9 “FLIPFLOP - Pulse Width and Phase Transient Calibration,”

page 68)

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Chapter 4. CRAMPS/Multipulse Module Operation

4.12 WaHuHa and WaHuHaHS - MP-Assisted High-Speed
Spinning (4-pulse cycle)

WaHuHa (Figure 25) is the original 4-pulse multipulse sequence. WaHuHAHS is a semi­windowless version of W aHuHa and is often used in conjunction with high speed spinning.
The sequences are applicable for UNITYplus and

acq

prep

pw

UNITY

INOVA.

d1

tau 2*tau

'np'/2 times

Figure 25. WaHuHa Pulse Sequence

tau

Macros

The macros wahuha and wahuhahs convert a S2PUL or FLIPFLOP data set for BR24.
cylmrev converts a data set for quadrature MREV8. All relevant parameters are preserved
if the initial data set is FLIPFLOP, BR24, CYLBR24, MREV8 or CYLMREV.

Parameters

pw is the 90o degree pulse-length, in microseconds.
tau is the interpulse delay , in microseconds, including pw. The WaHuHa cy cle is 6*tau

long and the W aHuHaHS is 4*tau+2*pw. They are repeated np/2 times to build up a FID.
tauc is the cycle time, in microseconds and is the actual dwell time for the FID. tauc is not

changed and is for information only.

71

mp_at is the sum of all cycles, in microseconds, and is the true acquisition time. mp_at
is not changed and is for information only.

sw=2e6 turns on the fast ADC without analog f ilters. sw does not determine the dwell time
(see tauc).

scalesw is a scale factor that converts sw=2e6 to the correctly scaled spectral width.
scalesw=(1.0/tauc*sw)*S where S is the multiple-pulse scale f actor for WaHuHa

(0.707 for ideal pulses).
rof1 and rof2 (see 4.9 “FLIPFLOP - Pulse Width and Phase Transient Calibration,”

page 68)

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

Chapter 5.

Solid-State NMR Accessories

Sections in this chapter:

• 5.2 “Rotor Synchronization Operation,” this page.

• 5.3 “Rotor Speed Controller Accessory Operation,” page 76.

• 5.4 “Variable Temperature Operation with Solids,” page 78

5.1 Pneumatics/Tachometer Box

The variable temperature (VT) Pneumatics/Tachometer Box is used with Varian VT CP/
MAS probes. The Pneumatics/T achometer Box handles all air/gas supply distribution to the
probe. The supply line is permanently connected to the wall supply, which must be clean,
dry air. The wall supply should be at a pressure not exceeding 120 psig (8 bar) and be
filtered to 0.6 micron.

CAUTION:

This section contains general information about the RT and VT Pneumatics/Tachometer
Boxes and installation instructions.

Figure 26 shows a Pneumatics/Tachometer Box for VT (variable temperature) CP/MAS

probes. This box is mounted on a leg of the magnet in a convenient position. The four hoses
coming out of the left side of the pneumatics box are connected to the probe ROTATION/
DRIVE, BEARING, BOD Y GAS, and the EJECT port of the magnet. These connectors are
of a high-pressure, quick-disconnec t type.

Failure to maintain a clean and dry air supply shortens probe life.

5.2 Rotor Synchronization Operation

In a number of experiments it is desirable to trigger an event at a precise point in the rotation
period of a rotor. Usually this is less relevant from transient to transient than it is within a
single transient. Even within a single transient, the required delay before the trigger point
may be some seconds or minutes. This delay is long enough for the rotor to change speed
enough so that “dead reckoning” is not sufficiently accurate. The rotor synchronization
accessory offers the spectroscopist the ability to synchronize events with the absolute
position of a CP/MAS rotor, as well as to read the rotor speed at any time.

Hardware Description

The rotor synchronization hardware detects the optical transition from dark to light of the
detection mark on a rotor and provides a pulse as a trigger to a circuit on the Acquisition
Controller or Pulse Sequence Controller board. Th e dark-to-ligh t edge can be used in three
ways:

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72

Chapter 5. Solid-State NMR Accessories

Flow meter/valveFilter

Rotation/drive to probe

Bearing to probe

Rotation trigger adjust

Body N2 to probe

To eject port

of magnet

Purge to heat exchanger

Angle adjust tool

Tachometer counter

Drive pressure
regulator and gauge

N2 supply in

Bearing pressure
regulator and gauge

Body pressure
regulator and gauge

Figure 26. Pneumatics/Tachometer Box for CP/MAS Probes

• The time between successive edges can be measured (note that the edges are alw ays in
the same sense, so that this interv al is on e ro tor p eriod ). Th is has a pr ecision of 50 ns.
This is shown as “mode 1" in Figure 27.

• An event can be triggered on the nth edge (in all cases here n is an integer). In this
mode, the rotor is providing an external timing event to the Acquisition Controller or
Pulse Sequence Controller board. This provides a means of delaying until the next
dark-to-light rotor edge. This is “mode 2" in Figure 27.

• The Acquisition Controller board or Pulse Sequence Controller board can be instructed
to delay precisely n rotor periods. This is done by interrupting an internal counter that
is normally reset at each rotor edge, delaying n edges and then counting the counter
down to zero. At this point the delay is finished. Thus, in principle, the error in the
delay will be only that percentage that the first and the last periods differ. This is sho wn
as “mode 3" in Figure 27.

Trigger on

2nd edge

Delay 5 periods

(mode 3)(mode 2)

73

Rotor period

= start of event = end of event

(mode 1)

Figure 27. Different Modes of the Rotor Synchronization Accessory

A potential source of error exists in determining the point of the light transition on which
to trigger the digital circuitry. This is a factor determined by two variables: the light
detection circuitry and the markings on the rotor.

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

5.2 Rotor Synchronization Operat io n

For light detection, the tachometer box provides the
light source and the detector . The rotor has a black ened
sector on its base (Figure 28) so that as it rotates,
differing amounts of light are reflected. The light is
transferred through light pipe to the stator base. The
reflected light is sampled by another light pipe and
brought back to the tachometer box where it is
photodetected. The resulting current is amplified and
used to toggle a Schmitt trigger that is the input to the
external time base of the Acquisition Controller or
Pulse Sequence Controller board.

In principle, detection in the Doty probe is the same. Figure 29 shows a Doty double­bearing rotor with a blackened sector on the inside of the lower drive cap. The light pipes,
however, are not as precise and the detection is more indirect, thus giving a lower signal­to-noise ratio.

The photodetection is performed in
the base of the probe and then
transferred to an external amplifier
with adjustable gain control. The
amplifier output is then sent to the
tachometer box where it is further
conditioned before being used to
drive the Acquisition Controller
board or Pulse Sequence Controller
board.

Figure 29. Doty Double Bearing Rotor

Figure 28. Base of a Varian

High-Speed Spinning Rotor

Specifications

The specifications for the rotor synchronization access ory depend on both the probe and the
electronics. The values given below reflect those that can be obtained in optimum
circumstances and, as such, do not imply a guarantee of performance. If performance is
severely de graded from these v alues, the fi rst remedy is to check the sector markings on the
rotor, because any lack of definition here will have profound effects on stability of the
result.

Varian High-Speed Spinning Probe

Jitter in one TTL rotor period (measured with an oscilloscope from falling edge to falling
edge) is
of
going transition of the reflected light going from at least a value of –39 dBm to no more
than –45 dBm, measured at the end of the fiber optics.

CAUTION:

≤ 500 ns for spinning speed s to 8 kHz. This correspond s to an angular un certainty

≤ 0.5° at a spinning speed of 3600 Hz. An edge is detected normally as the negative-

Never spin PSZ (zirconia) rotors (white or off white in color) above 7.5
kHz or silicon nitride rotors (gray ) above 9 kHz. High spinning sp eeds
will cause the rotors to shatter.

Doty Scientific Probe

Jitter in a TTL rotor period is ≤ 2 µs for spinning speeds to 5 kHz. This corresponds to an
angular uncertainty of
temperature range of –50
correctly adjusted to give a signal of no less than 1 Vpp into the tachometer box.

≤ 2° at a spinning speed of 3600 Hz. This is expected over the

°C to +100 °C, provided that the tachometer amplifier gain is

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74

Chapter 5. Solid-State NMR Accessories

Using Rotor Synchronization

Table 10 lists parameters used with the rotor synchronization accessory.

Table 10. Rotor Synchronization Controls

Parameters

hsrotor {'y', 'n'} Display rotor speed for solids operation
in {'y', 'n'} Interlock
srate {0–107, in Hz} Spinning rate for magic angle spinning

The rotor synchronization accessory can be used in a number of ways, from simple
monitoring of spinning speed to sophisticated synchronized experiments. In all cases, the
accuracy of the readout is dependent on the marking of the sectors on the rotor. Figure 28
shows the marking on the base of Varian high-speed spinning rotors a nd Figure 29 shows
the marking inside the lower rotor cap for Doty rotors.

Rotor Markings

For Varian high-speed spinning rotors, the base of zirconia rotors may be bl ack ened using
a black permanent marker . Mak e sure that the di viding line acr oss the diameter is clear and
that the black sector is solid black. The base of silicon nitride rotors may be whitened
similarly using typewriter correction fluid. Avoid using a water-based correction fluid
because it is more likely to spin off the rotor. White paint can also be used.

For Doty rotors, use the supplied black and white paints. Ensure that the dividing line
between black and white is sharp. Periodically check that the black and white markings are
still sharp. Over time, the high spinning speeds may cause the paint to “fly off.” Repaint the
rotors when needed.

Sample Spinning

The sample is packed in the rotor in the normal way. The ro tor is spun in accord ance with
the instructions in “Spinning the Sample,” page 22, and the spinning speed may be read on
the tachometer box LCD display. Note that for Varian probes, the optical fibers should be
plugged into the tachometer box, a nd for Doty probes the prob e should be co nnected to the
Doty tachometer amplifier, the switch on the amplifier set away from the OPTICAL OFF
position, and the OPTICAL OUT BNC connected with a coax cable to the EXTERNAL
INPUT of the tachometer box.

Spinning Speed

The parameter hsrotor is an experiment-based parameter, not a globally accessible
parameter. If you join another experiment to do rotor synchronization, hsrotor may also
need to be created in that e x perimen t. Th e spinning speed of the rotor may be displayed in
the ACQUISITION ST ATUS window if the parameter hsrotor is set to 'y'. If the speed
does not show, enter hsrotor?

If hsrotor is undefined, enter create('hsrotor','string'), and then enter
hsrotor='y' su to acti vate the spinning speed display. Once the setup is complete, the
correct rotor speed should appear in the Acquisition Status window. This checks that the
rotor sync accessory is working.

75

CP/MAS operates in the normal manner with rotor synchronization installed. Manual entry
of srate (spinning speed in Hz) is accepted; however, srate is updated at the end of
each acquisition to reflect the actual spinning speed at the end of the acquisition. At the start

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

5.3 Rotor Speed Controller Accessory Operation

of each acquisition, the initial spinning speed is noted. If, during acquisition, the speed
alters by more than 100 Hz and the interlock parameter in is set to 'y', acquisition is
halted.

The flexibility of rotor synchronization is mainly through the construction of pulse
sequences using rotor sync elements (refer to the VNMR User Programming Manual for
information on creating pulse sequences).

5.3 Rotor Speed Controller Accessory Operation

The Varian rotor speed controller accessory provides computer contro l of the spin rate of a
CP/MAS sample. By using the controller in a closed loop mode, the sample spinning rate
can be held constant to a few hertz or better over a long acquisition time (days or weeks).
During variable temperature operation, the rotor controller can keep the spin rate from
changing while varying the operating temperature. The setting of a desired rate is much
easier because fine control is provided for and slow drift is automatically compensated.

Rotor Speed Controller Hardware

The rotor speed controller accessory consists of the following hardware:

• Modified Varian VT pneumatics/tachometer box

• PC-compatible computer with 16-bit timer-counter and DAC cards

• Cabling to connect PC, pneumatics/tachometer box, and Sun workstation

The use of a PC computer provides an inexpensive, powerful, and dedicated processor for
rotor speed controlling tasks. The PC houses 16-bit DAC and counters for measuring the
rotor speed and supplying a 0 to 5 V signal to the pneumatics transducer in side the
pneumatics/tachometer box. Operator con trol of the PC and software tak es place through a
RS-232 link to the Sun host computer.

Rotor Speed Controller Software

The rotor controller is run with the rcontrol software, which has a menu driven
interface. The main menu provides choices that initiate the following:

• Open loop

• Closed loop

• Configuratio n routines

• Exit from the rcontrol software

Open Loop Mode

In open loop (O) mode, t he program requests a DAC value (0 to 65385) and then
continually displays the rotor speed on the screen. Open loop mode is useful when spinning
a sample up f o r th e first time—perhaps, to check packing balance—or to calibrate the
electro-pneumatic regulator span and zero settings.

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Chapter 5. Solid-State NMR Accessories

The DAC value can be changed while con tinuo us ly dis playin g the ro tor s peed b y pres sing
the following keys and simulta neous key combinations on the PC keyboard:

Actions Keys

Decrease DAC value by 1 unit f
Decrease DAC value by 100 units l
Decrease DAC value by 1000 units Shift-l
Increase DAC value by 1 unit Shift-f
Increase DAC value by 100 units h
Increase DAC value by 1000 units Shift-h
Exit to main menu q

Closed Loop Mode

In closed loop (C) mode, the desired rotor speed is entered. The control algorithm then
takes over to control the rotor speed. While controlling is active, the DAC value, latest
increment to the DAC, and the d if ference of th e rotor speed and the s et point are displayed
each time through the control loop.

To stop the speed control process, press the q key. After the process is stopped, you can
enter a new rotor speed, save the data log file, or exit to the main menu.

To save the data log file (DA C and rotor speed v alues), choose the L option from the main
menu. You can specify the number of data points to log (4000 points maximum) and a
control loop divisor N. For example, if N is set to 10, a D AC and rotor speed pair is logged
every 10th time through the control loop. Log data is written to disk only after termination
of the closed loop control session and confirmation by the user.

Configuration Routines

The configuration (F) choice at the main menu displays the current gain settings used in the
closed loop control process and allows you to change them. Besides the gain values, the
configuration routines allow you to set the following:

• Loop delay , set in milliseconds

• Increment clamp value for the loop increment

The loop delay specifies a time delay between outputting to the DA C an d reading the rotor
speed. Note that too short a time may lead to wild oscillations in the closed loop mode when
the gain settings are large.

The increment clamp value sets the maximum change to th e DA C wor d and is a useful type
of “adaptive gain” that can allow gain settings that produce good control so long as th e
change in set point is not too large.

T ypical ranges for the gain settings are shown in Table 11. G3 and G4 set to 0 pro duce good
control when the ranges shown in the table are used for the other gains.

77

Table 11. Rotor Controller Gain Setting and Typical Ranges

Gain Setting Typical Ranges

G1 4 to 5
G2 1 to 2

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

5.4 Variable Temperature Operation with Solids

Gain Setting Typical Ranges

G3 0
G4 0
G5 0.5 to 1, with a loop delay of 500 to 700 ms and

an increment clamp of 5000

The configuration parameters can be saved to a file on the PC (e.g., gain.set). Upon
initial startup, the parameters in this file are loaded in order to set the configuration. Be sure
to make copies of the configuration parameters file (gain.set), or write down the current
settings if you wish to experiment with changing the rotor control configuration.

Additional Operation Note

The PC computer has been set up such that a monitor and keyboard is not required in order
to pass the POST (Power On Self Diagnostics) test, which occurs before the operating
system is loaded from disk. These op tions are set into the CMOS BIOS setup at the factory .
If the CMOS fails for some reason, the BIOS setup will have to be reconfigured.

The most likely cause for CMOS failure is drainage on the battery that powers the CMOS
when the computer is off. This battery is continuously recharged while the computer is on,
so even if the rotor speed controller is not in use, it is wise to keep the computer powered up.

If the computer does need to be turned off, do not leave it off for extended periods of time
(weeks or months). If the CMOS does lose its memory settings, a video card, PC monitor,
and keyboard will ha ve to be attached so that the CMOS set up program (not part of DOS)
can be run.

5.4 Variable Temperature Operation with Solids

This section provides general instructions on the solids variable temperature (VT)
accessory. The accessory installation manual for the system provides more detailed
instructions on solids VT.

Varian Solids VT System

The Varian solids variable temperature accessory (Part No. 00-9589 94-00) can be ad ded to
a Varian VT CP/MAS probe for VT operation. When this accessory is added, connection
of the gas supplies to the probe is altered in the following ways.

• Body nitrogen is needed whenever the probe is in operation. The connection of the VT
gas supply is described in the VT installation manual.

• The VT controller is connected to a booster power supply and th e booster power supp ly
is connected to the probe. This is accomplished with the solids VT cable as described
in the VT installation manual.

• The liquids upper barrel is pushed down so it touches the top of the probe. This,
together with the Varian bore vent assembly, serves as the exhaust stack.

• VT operation requires the use of Torlon end caps.

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Chapter 5. Solid-State NMR Accessories

Doty Solids VT System

The Varian solids VT accessory can also be added to the Doty CP/MAS probe for VT
operation. When this accessory is added, connection of the gas supplies to the probe is
altered in the following ways:

• Body cooling gas is also needed whenever the probe is not at ambient temperature.
Connect the VT gas supply to the probes is made as described in the Doty manual.

• The VT controller is connected to the boost supply and the boost supply is connected
to the probe.

• The liquids upper barrel is pushed down so it touches the top of the probe. The upper
barrel then acts as an exhaust stack.

VT operation requires V espel end caps. Vespel is less susceptible to thermal deformation at
high temperatures and has a lower coefficient of expansion, so is less likely to slip out at
low temperatures.

Changes in temperature should al ways be k ept small because rapid changes can cause rotor
crashing.

79

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

Chapter 6.

Sections in this chapter:

• 6.1 “XPOLAR—Cross-Polarization, UNITY,” page 81

• 6.2 “XPOLAR1—Cross-Polarization,” page 85

• 6.3 “XPWXCAL—Observe-Pulse Calibration with Cross-Polar ization,” page 87

• 6.4 “XNOESYS YNC—Rotor Sync Solids Sequence for Exchange,” page 89

• 6.5 “MASEXCH1—Phase-Sensitive Rotor Sync Sequence for Exchange,” page 90

• 6.6 “HETCORCP1—Solid-State HETCOR,” page 92

• 6.7 “WISE1 —Two-Dimensional Proton Wideline Separation,” page 93

• 6.8 “XPOLWFG1—Cross-Polarization with Programmed Decoupling,” page 93

• 6.9 “XPOLXMOD1—Waveform Modulated Cross-Polarization,” page 95

• 6.10 “VACP—Variable Amplitude Cross-Polarization,” page 97

• 6.11 “XPOLEDIT1—Solids Spectral Editing,” page 98

• 6.12 “3QMAS1—Triple-Quantum 2D for Quadrupole Nuclei,” page 99

• 6.13 “PASS1—2D Sideband Separation for CP/MAS,” page 101

• 6.14 “ CPCS—Cross-Polarization with Proton Chemical Shift Selection,” page 102

• 6.15 “CPCOSYPS—Cross-Polarization Phase-Sensitive COSY,” page 103

• 6.16 “CPNOESYPS—Cross-Polarization Phase-Sensitive NOESY,” page 104

• 6.17 “R2SE LPULS1—Rotation Resonance w ith Selective Inversion,” page 106

• 6.18 “ DIPSHFT1—Separated Local Field Spectroscopy,” page 108

• 6.19 “SEDRA2—Simple Excitation of Dephasing Rotational-Echo Amplitudes,” page 109

• 6.20 “REDOR1—Rotational Echo Double Resonance,” page 111

• 6.21 “DOUBLECP1—Double Cross-Polarization,” page 113

• 6.22 “T1CP1—T

• 6.23 “HAHNCP1—Spin 1/2 Echo Sequence with CP,” page 116

• 6.24 “ SSECHO1—Solid-State Echo Sequence for Wideline Solids,” page 117

• 6.25 “WLEXCH1—Wideline S olids Exchange,” page 119

• 6.26 “HS90—90-Degree° Phase Shift Accuracy,” page 121

• 6.27 “MREVCS—Multiple Pulse Chemical-Shift Selective Spin Dif fusion, ” page 122

• 6.28 “MQ_SOLIDS—Multiple-Quantum Solids,” page 123

• 6.29 “SPINDIFF—Spin Diffusion in Solids,” page 124

• 6.30 “ FASTACQ—Multinuclear Fast Acquisition,” page 124

• 6.31 “NUTATE—Solids 2D Nutation,” page 125

Solid-State NMR Experiments

Measurement with Cross-Polarization,” page 115

1

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

80

Chapter 6. Solid-Sta te NMR Experi ments

This chapter describes CP/MAS, triple-resonance, wideline, and multipulse pulse
sequences for solid-state NMR. To aid in identification, the names of pulse sequences are
given in all capital letters. In general, most of these experiments are intended for

UNITY

INOV A and UNITYplus systems. Running these sequences on UNITY, and VXR-S

systems may require some modifications. None of these sequences are available on

ERCURY and GEMINI 2000 systems.

M

The macros for some of the solid- state NMR sequences are located in maclib. The macros
for other solid-state NMR sequences are located in the user library userlib.

User Library—Terms and Conditions

Material submitted to the user library is distributed by Varian as a service to its
users. All rights to the material submitted are retained by the submitter, unless
explicitly surrendered in the accompanying README document.

You may not redistribute anything in the user library in any form to anyone outside
of your own organization, without the express permission of the submitter.

Neither V arian, Inc. nor the submitter makes any warranty or representation of any
kind, express or implied, with respect the material found in the user library.

This material is distributed “as is,” and you as sume the entire ris k as to the qu ality,
reliability, and performance of any software you choose to use.

In no event shall Varian, Inc. be liable for any consequential, special, incidental,
direct, or indirect damages of any kind aris ing out of the use o f software in th e user
library.

Use of any material in the user library shall constitute acceptance of these terms and
conditions.

6.1 XPOLAR—Cross-Polarization, UNITY

XPOLAR is the basic sequence for CP/MAS, MAS and solid-state relaxation
measurements for UNITY systems ( for
XPOLAR can be run either as a standard single pulse experiment, including the inversion
recovery experiment, with the parameter xpol set to 'n', or more typically as a cross-
polarization experiment, with the parameter xpol set to 'y'. The use of the XPOLAR
sequence allows the r emo val of strong dipolar coupling by usin g a s trong d ecoup ling field
applied during the acquisition of the data.

A characteristic of some nuclei in the solid state, for example
relaxation time (T

). T o overcome this problem, the abundant nuclei (usually protons) in the

1

systems are polarized with a spin locking pulse and the polarization is then transferred to
the rare spins by applying an rf fi eld at the Larmor frequency of the r are spins that is of such
magnitude as to make the energy levels of the abundant and rare spins the same in the
rotating frame, the Hartmann-Hahn match condition. Following a transfer of energy from
the polarized spins to the rare spins, the rare-spin field is turned off and resulting signal
observed under conditions of high-power proton decoupling. The recycle time is then set
according to the proton T

, usually much shorter than the rare-spin T1.

1

For samples that use cross-polarization, the “contact” time (the time during which cross­polarization occurs) should be optimized with the parameter p2. This is necessary because

UNITY

INOV A and UNITYplus systems, see page 85).

13

C, is a long spin-lattice

81

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

6.1 XPOLAR—Cross-Polarization, UNITY

two processes happen simultaneously, the magnetization buildup from cross-polarization
and the magnetization loss from rotating-frame relaxation. A time exists for which an
optimum in the magnetization occurs. The rising and falling exponential intensities can be
analyzed with the contact_time macro, which calculates both T

and 1H T

CH

1ρ

.

Applicability

XPOLAR is available on all systems.

Suppressing Spinning Sidebands

NMR spectra at high magnetic fields often have significant spinning sidebands. While these
spinning sidebands contain informati on about the chemical shift anisotropy, they can
complicate the interpretation of complex spectra. The sidebands can be eliminated using
the TOSS (TOtal Sideband Suppression) technique. The TOSS pulse sequence is selected
by setting toss='y'. Note that the parameter srate should be set to the spinning speed
in Hz. TOSS uses 180
to optimize the TOSS experiment. Figure 30 shows the pulse sequence diagram for cross­polarization with TOSS.

° pulses based on the param eter pw. It may be necessary to adjust pw

xpol='y' toss='y'

d1

1

H

13

C

pw

level1

p2

Delay recipe
including

level2

srate

Figure 30. TOSS Pulse Sequence

Suppression of Protonated Carbons (Interrupted Decoupling)

Off-resonance decoupling and related experiments, such as DEPT, in which J-coupling is
involved are not usually possible in solids because through-space dipolar coupling as well
as J-coupling is present. An experiment exists, however, that can be used to discriminate
between protonated and non protonated carbo ns—this is th e protonated carbon s uppression
experiment of Opella and Fry. In this experiment, the decoupler is turned off before
acquisition to dephase the protonated carbons.

The technique is effecti ve for non-mo bile carbons. Mobile carbo ns, like meth yl groups, are
typically not suppressed as well. The experiment is run by setting pdp='y', setting
srate to the spinning speed and entering appropriate values fo r the dephasing time d2 (i n
seconds). Figure 31 shows the pulse sequence diagram for cross-polarization with
interrupted decoupling.

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Chapter 6. Solid-Sta te NMR Experi ments

xpol='y' pdp='y'

pw

d1

1

H

level1

p2

level2

2*pw

13

C

d2

1/srate

1/srate

Figure 31. Protonated Carbon Suppression Sequence

Measurement of 13C T

1ρ

Measurements of the spin-lattice relaxation time in the rotating frame (T1ρ) are possible
using the standard XPOLAR pulse sequence. The parameter p3 is the spinlock time after
cross-polarization. Typical values for p3 range from 50 to 50 00 microseconds. Figure 32
is a diagram of the sequence.

1

13

xpol='y'

H

C

d1

pw

level1

p2

p3

level2

83

Figure 32. Rotating-Frame Spin-Lattice Relaxation Measurements Sequence

To analyze a T

analyze('expfit','p3','t2','list').

experiment of the decay time constant, enter:

1ρ

The analyze command has four arguments. The first argument is expfit. The
analyze program provides an interface to the curve fitting program expfit, supply ing
it with the input data in the form of a text file analyze.inp in the current experiment.
analyze.inp is generated by a line listing of the peaks of interest in a spectrum and by
the fp command, which measures the peak he ight of each peak in an array of spectra. Th e
second argument of analyze is the name of the arrayed parameter, which in the case of

13

C T

ρ experiments usin g the xpolar sequence is the parameter p3 (for xpolar1, use

1

pchro). The third argument is the type of analysis to be performed, for example use t2
for the exponentially decreasing data points of a T

ρ experiment. The fourth argument,

1

list, results in the construction of the file analyze.list, where the summary of the
data analysis and calculations are stored in the current experiment. A hard copy can be

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

6.1 XPOLAR—Cross-Polarization, UNITY

obtained just as with any other text file. The graphical display of the data can be viewed on
screen by using the command exp1 or plotted with the command pexp1.

Measurement of the 1H

T

through Cross-Po larization

1

Proton T1 can be measured using the XPOLAR pulse sequence by performing a standard
inversion-recovery experiment on the protons followed by cross-polarization of the
remaining

1

H magnetization to the carbons. Figure 33 is a diagram of the pulse sequence.

The xpolar macro sets up parameters for the XPOLAR pulse sequence.

level2

1

1

13

xpol='y'

H

C

d1

p1

d2

pw

Figure 33. Pulse Sequence for Measuring lH T

level1

p2

Parameters

xpol is set to 'n' for direct polarization or set to 'y' for cross-polarization.
pw is the observe pulse for direct polarization or the proton 90

° pulse for cross-polarization.

pw is in microseconds.
p1 is the initial observe pulse (direct polarization), usually set to a 180°° inversion pulse,

or the initial proton pulse, usually set to a 180

° pulse (cross polarization). p1 is in

microseconds.

p2 is the cross-polarization contact time, in microseconds.
p3 is a pulse, in microseconds, for an X-nucleus only spin-lock following p2.
dm should be set to 'nny'. The decoupler has a maximum duty cycle of 20%.
d2 is delay between p1 and pw (for inversion- recover y) if pdp='n'. If pdp='y', d2 is

a delay for interrupted decoupling for protonated carbon suppression. d2 is in seconds.
srate is the sample spinning rate, in Hz.
toss set to 'y' invokes timed spin-echoes to suppress s pinning side bands.
level1 controls decoupler power during cross-polarization.
level1f controls fine decoupler power during cross-polarization.
level2 controls decoupler power during acquisition.
level2f controls fine decoupler power during acquisition time.
level1 and level2 control decoupler power and should be used for Hartmann-Hahn

matching. The decoupler is set with the config display and can be either class C, with a

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84

Chapter 6. Solid-Sta te NMR Experi ments

maximum level of 255, or linear, with a maximum of 63. 0 is the minimum power on

UNITY

UNITY systems and –16 is the minimum on

INOV A and UNITYplus systems.

level1f and level2f are only active for linear attenuators and they give an additional

UNITY

6 dB range for UNITY systems and 60 dB range fo r

INOVA and UNITYplus systems,

divided into 4095 steps. level1 and level2 override dpwr.

References

Cross-Po larization Technique

Pines, A.; Gibby, M. G.; Waugh, J. S. J. Chem. Phys. 1973, 59, 569.
Stejskal, E. O.; Schaefer, J.; Waugh, J. S. J. Magn. Reson. 1977, 28, 105.

Spinning Sideban ds

Herzfeld, J.; Berger, A. E. J. Chem. Phys. 1980, 73, 6021.
Dixon, W. T. J. Magn. Reson. 1981, 44, 220.
Dixon, W. T. J. Magn. Reson. 1982, 49, 341.
Dixon, W. T. J. Magn. Reson. 1985, 64, 332.

Protonated Carbon Suppression

Opella, S. J.; Fry, M. H. J. Am. Chem. Soc. 1979, 101, 5856.

Relaxation Times

Schaefer, J.; Stejskal, E. O.; Buchdahl, R. Macromolecules 1077, 10, 384.

6.2 XPOLAR1—Cross-Polarization

XPOLAR1 is applicable to MERCURYplus, MERCURY-VX,
newer UNITY systems. The parameters that control the attenuators and linear modulators
are shown in the diagram of XPOLAR1, see Figure 34.

cntct

(tpwrm)

Tx

pw

d1

Dec

cntct

(crossp)

UNITY

at

(dipolr)

INOVA, UNITYplus, and

85

AC

Figure 34. XPOLAR1 Pulse Sequence

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

6.2 XPOLAR1—Cross-Polarization

Cross-polarization amplitudes should be controlled using the fine attenuator. The fine
attenuator has a range of 60 dB for Ino va and 48 dB for MERCURY systems down from the
course attenuator. The coarse attenuator is set to a value corresponding to the maximum
specification of the probe. Cross-polarization on the UNITY requires the use of both the
coarse and fine attenuators (6 db range).

Applicability

XPOLAR1 can be found in /vnmr/psglib. The MERCURYplus and MERCURY-VX

UNITY

version of XPOLAR1 is not interchangeable with XPOLAR1 for

INOVA and
UNITYplus systems. UNITY systems can use both XPOLAR1 and XPOLAR by setting
dblvl2=’y’.

Macro

When this macro is run on a
convert s parameters for XPOLAR and most ot her double- and triple-resonance solids pulse
sequences for the XPOLAR1 pulse sequence. Power parameters are left unchanged.
Parameters irrele vant to XPOLAR1 are remo ved. On MERCURY-VX or MERCURYplus the
macro XPOLAR1 will convert parameters contained in experiments run on
UNITYplus, and UNITY when these data sets are loaded on the system and the macro is
run.

For users familiar with
following:

• If the UNITY power parameters are defined (in an XPOLAR parameter set),
they are converted to the corresponding
parameters: (level1=cppwr level2=dpwr level1f=crossp
level2f=dipolr p2=cntct tpwrf=tpwrm) and dblvl2 is set to 'n'.
If dblvl2=’y’, both cppwr and dpwr are used. If dblvl2=’n’, cppwr is not used
and dpwr=cppwr.

• xpolar1 does not convert an arbitrary parameter set for solids. First retrieve a
solids parameter set (e.g., xpolar.par in the VNMR directory parlib) and
then convert it with the xpolar1 macro.

UNITY

INOV A, UNITYplus, and UNITY, the macro xpolar1

UNITY

UNITY

INOVA, UNITYplus, and UNITY solids, note the

UNITY

INOVA and UNITYplus

INOV A,

Parameters

• xpol is set to 'n' for direct polarization or xpol is set to 'y' for cross- polarization.

• pw is the observe pulse for direct polarization, or the proton 90
polarization. pw is in microseconds.

• pwx is th e obser ve 90

o

pulse, used for TOSS and dipolar dephasing, pwx is in

microseconds.

• cntct is th e cross-po lar ization contact time, in microseconds.

• tpwr is th e obser ve power setting .

Spectrometer Minimum, dB Maximum, dB

INOVAcpmas -16 63
MERCURYcpmas 063

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

° pulse for cross-

86

Chapter 6. Solid-Sta te NMR Experi ments

• tpwrm is th e observe linear modulator setti ng .

Spectrometer Minimum Maximum

INOVAcpmas 0 4095
MERCURYcpmas 0 255

The parameter tpwrm is linearly proportional to the applied transmitter voltage—
doubling tpwrm halves the value of the pulse width.

• dpwr is the decoupler power setting for decoupling throughout the acquisition period .

Spectrometer Minimum, dB Maximum, dB

INOVAcpmas -16 63
MERCURYcpmas 063

• cppwr (UN ITY only) is th e decoupler power setting for cross polarization when
dblvl2=’y’.

• dipolr is the decoupler linear modulator setting during acquisition (0 minimum
voltage to 409 5 for INO VA or 255 for MERCURY series maximum voltage). The value
of dipolr is linearly proportional to the applied decoupler voltage—doubling
dipolr doubles the decoupler field strength (in kHz).

• dblvl2 (UNITY only) is set to ‘y’ to obtain the parameter cppwr.

• crossp is the decoupler lin ear modulator setting during cross-polarization and the
initial 90
maximum voltage). The range is similar to dipolr. Doubling crossp doubles the
cross-polarization field strength (in kHz) and halves the initial proton 90

• p180 greater than 0.0 implements an additional prepulse, followed by a delay d2. For
direct polarization (xpol='n'), p180 is an observe pulse. For cross-polarization
(xpol='y'), p180 is a proton pulse. p180 is in microseconds.

• pcrho greater than 0.0 implements an additional observe pulse following the contact
time. Use pcrho for observe T
microseconds.

• dm should be set to 'nny'. The decoupler has a maximum duty cycle of 20%.

• pdp set to 'y' im plements interrupted decoupling for a period pdpd2 to cause
suppression of protonated carbons.

• pdpd2 is set greater then 0.0 (see pdp), pdpd2 is in microseconds

• d2 is set greater than 0.0 (see p180), d2 is in seconds.

• srate is th e sam ple spinn in g speed, in Hz.

• hsrotor set to ‘y’ allows automatic update of the value of srate if automatic
spinning speed control is used.

• toss set to 'y' implements timed spin echoes to suppress spinning side bands.
Timing is determined from the value of srate.

Note that for toss='y' or pdp='y', srate must be set correctly because delays
are calculated from 1.0/srate.

° pulse (0 minimum voltage to 4095 for INOVA or 255 for MERCURY serie s

measurements. The units for pcrho are

1ρ

° pulse.

6.3 XPWXCAL—Observe-Pulse Calibration with
Cross-Polarization

The pulse sequence XPWXCAL, deri ved from XPOLAR1, is used to calibrate the observ e

° pulse if observe pulses are to be used explicitly in pulse sequences. Because cross-

90

87

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

6.3 XPWXCAL—Observe-Pulse Calibratio n with Cross -Polarization

polarization is used for preparation, XPWXCAL can be run in less time than XPOLAR1
with xpol='n'. Figure 35 is a diagram of the sequence.

<if phase=2>

cntct

(tpwrm)

pwx

Tx

Dec

YX

d2

pw

d1

AC

cntct

(crossp)

at

(dipolr)

Figure 35. XPWXCAL Pulse Sequ ence

Applicability

XPWXCAL is available only on

UNITY

INOVA and UNITYplus. It is found in userlib.

Macro

The macro xpwxcal conver ts a parameter set, obtained with XPOLAR or XPOLAR1, for
the XPWXCAL exper iment. Po wer l ev els and t he proton 90°
default, pwx=pw and phase=2.

° pulse width are retained. By

Parameters

xpwxcal uses the
cppwr, dipolr, crossp, dblvl2, pw, and cntct. See page 85 for a description of

these parameters.
pwx is the observe 90°

rotates the observe magnetization to the minus z axis and nulls the NMR signal. Array pwx
between the 0

°, null for 270°, and positive for 360°.

for 180
When the Hartmann-Hahn conditi on is matched for a non-sp inning samp le, the proton 90

pulse pw equals pwx. In the presence of spinning, a match that causes maximum spectral
intensity will be offset in power above or below the true Hartmann-Hahn condition. If
observe pulses are used explicitly in a sequence (TOSS, REDOR1, HETCORCP1, etc.)
pwx must be measured separately, and it is usually present as a separate parameter. For
HETCORCP1, pwx must be set to pw (by adjusting tpwrm), and pw is used for both
observe and proton pulses.

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

UNITY

INOVA and UNITYplus parameters tpwr, tpwrm, dpwr,

° pulse length. pwx follows the contact time and, when set to 90°,

° and 360° pulse. The f irst null is the observe 90° pulse. The signal is negative

88

°

Chapter 6. Solid-Sta te NMR Experi ments

phase=2 sets the phase of pwx 90° to the contact pulse and is necessary for measurement
of pwx. Setting phase=1 sets the two phases the same, and all array members of a pwx
array have the same intensity.

6.4 XNOESYSYNC—Rotor Sync Solids Sequ ence fo r Exchange

The XNOESYSYNC sequence is the CP/MAS equivalent of a NOESY, but with the first

° pulse replaced with cross-polarization. Unlik e normal NOESY, the mixing time can be

90
rotor synchronized. In the solid state, e xchange can occur via the spinning sidebands unless
the mixing time is synchronized to the rotor period. When this is done, cross peaks appear
when self or chemical exchange occurs. Figure 36 is a diagram of the sequence.

Rotor

1

13

d2

90 p2

H

p2

C

cp90 cp90

d2

mix at

pw

Figure 36. XNOESYSYNC Pulse Sequence

Macro

The xnoesysync macro sets up parameters for the XNOESYSYNC pulse sequence.

Parameters

89

pw is the 1H 90° pulse, in microseconds, for cross-polarization.
p2 is the contact time, in microseconds.
d2 is the evolution time, in seconds.
dm is set to 'nny' for no proton decoupling during the mixing time, or dm is set to 'nyy'

for proton decoupling during the mixing time.

level1 controls decoupler power during cross-polarization.
level1f controls fine decoupler power during cross-polarization.
level2 controls decoupler power during acquisition.
level2f controls fine decoupler power during acquisition time.
phase is 0 for P type, phase is 1 for N type, or phase is 1,2 for phase sensitive. The

Veeman experiment requires phase=0.

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

6.5 MASEXCH1—Phase-Sensitive Rotor Sync Sequence for Exchange

cp90 is the 13C 90° pulse, in microseconds.
mix is the mixing time, in seconds.
sync is set to 'y' to run rotor with sync; sync is set to 'n' to run unsynchronized

(normal NOESY).

Technique

The minimum phase cycle is 16 transients and the full cycle is 64 transients.
The synched experiment requires SSBs to be present, so the spin rate should be slow

enough.
Because the mix time is recalculated on the basis of the number of integral rotor periods

that is nearest to the desired mix time, mix will not be exactly correct. The correct value is
calculated and printed at go time.

Normally, the sync experiment is run as a P-type experiment. Process the data with sinebell
weighting, wft2d('ptype') and foldt.

References

Szeverenyi, N. M.; Sullivan, M. J.; Maciel, G. E. J. Magn. Res. 1982, 47, 462.
DeJong, A. F.; Ketgens, A. P. M.; Veeman, W. S. Chem. Phys. Lett. 1984, 109, 337.

6.5 MASEXCH1—Phase-Sensitive Rotor Sync Sequence f or
Exchange

MASEXCH1 is a rotor-synchronized CP/MAS exchange sequence similar to
XNOESYSYNC, except that this sequence can yield a phase-sensitive spectrum rather than
an absolute-value plot. This experiment should be run under slow spinning conditions since
spinning sidebands intensities carry the informatio n. A n orm al MAS spectrum, including
sidebands, is obtained along the diagonal. Cross-peaks appear when solid-state chemical
exchange or molecular reorientation is present. Figure 37 is a diagram of the sequence.

Applicability

MASEXCH1 is available on
requires a rotor-synchronization accessory. Rotor-speed control is also recommended. On
request, a related sequence C13EXCH is available for older systems.

Macro

The macro masexch1 con verts a parameter set obtained with XPOLAR or XPOLAR1 for
the MASEXCH1 experiment. Power levels and pulse widths are retained. The default is

phase=1,2,3,4 and the data are transformed with wft2d(1,0,0,1,1,0,0,­1,0,-1,1,0,0,1,1,0).

UNITY

INOVA and UNITYplus and present in userlib. It

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Chapter 6. Solid-Sta te NMR Experi ments

sync='y'
mix = n/srate for phase=1,2
mix =n/srate-d2 f or pha se =3,4

pwx

Tx

Dec

cntct

(tpwrm)

d2

pw

d1

AC

cntct

(crossp)

pwx

mix

(dipolr)

Figure 37. MASEXCH1 Pulse Sequence

Parameters

MASEXCH1makes use of the
dpwr, cppwr, dipolr, crossp, dblvl2, pw and cntct. See page 85 for a
description of these parameters.

UNITY

INOVA and UNITYplus parameters tpwr, tpwrm,

at

91

pwx is the observe 90

° pulse in microseconds.

phase is 1,2 for P type, the Veeman experiment, for transformation with
wft2d(1,0,0,1,0,-1,1,0) and 1,2,3,4 for the phase sensitive spectrum
according to the reference for transformation with wft2d(1,0,0,1,1,0,0,

-1,0,-1,1,0,0,1,1,0). The phase-sensitive spectrum is the sum of a Veeman
experiment, phase=1,2 and a time-reversed experiment, phase=3,4.

mix is the mixing time, in seconds. For phase=1,2,3,4 the minimum mixing time is
equal to (ni-1/sw1). For phase=1,2 the minimum mixing time is 0.0.

sync='y' to run with rotor synchronization. sync='n' to run unsynchronized (normal)

NOESY.
nt is a minimum of 16.

Reference

Luz, Z.; Spiess, H. W.; Titman, J. J. Israel J. of Chem. 1992, 32, 145.

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

6.6 HETCORCP1—Solid-State HETCOR

6.6 HETCORCP1—Solid-State HETCOR

HETCORCP1 is a 1H –13C heteronuclear chemical shift correlation (HETCOR)
experiment for solid-state materials. Analogous to solution-state HETCOR experiments,
this sequence provides correlation between
experiment differs from the solution-state HETCOR in that correlation depends on dipolar
interactions rather than J coupling.

Applicability

HETCORCP1 is available on
psglib.

UNITY

INOVA, UNITYplus, and UNITY systems. It is found in

Macro

The macro hetcorcp1 con verts a parameter set, obtained with XPOLAR or XPOLAR1,
for the solids HETCOR experiment HETCORCP1. Power levels and the proton 90
width are retained. Default parameters set up for a phase-sensitive hypercomplex data set
acquisition. The correct sw1 is calculated and srate is set to the preferred value. Set the
actual spin rate equal to srate. A single decoupler offset dof is used throughout.

1

H and 13C chemical shifts. The HETCORCP1

° pulse

Parameters

hetcorcp1 uses the
cppwr, dipolr, crossp, dblvl2, pw, and cntct. See page 85 for a description of

these parameters.
setup is set to 'n' to obtain a 2D spectrum (normal operation). Set setup='y' to

obtain a single t
to 'y' to obtain a one-dimensional spectrum using a “proton chemical shift selectio n
pulse” or to observe the pulse sequence with dps for ni greater than 1.

pw is both the

1

tpwrm (using xpwxcal) to make the pulse lengths equal.
wim is the number of WIM-24 cycles used for cross-polarization. For best results, set the

length of the WIM-24 cross-polarization to occupy one-half a rotor period, for example,
wim=1, pw=4.0, and srate=5208 yields 96 microseconds of CP and a rotor cycle of
192 microseconds.

srate is the actual rotor speed (see wim above) . It is preferable, b ut not necess ary, to use
rotor speed control.

bmult is the number of BLEW -12 cycles per f

1.0/(bmult*12*pw*1e-6). Default values are bmult=2 for phase=1,2
(hypercomplex), alternatively bmult=1 for phase=3 (TPPI).

phase=1,2 for the hypercomplex method (use wft2da for the 2D FT); phase=3 for
TPPI (use wft2d(1,0,0,0) for the 2D FT).

UNITY

INOVA and UNITYplus parameters tpwr, tpwrm, dpwr,

FID, blew is the number of BLEW-12 cycles. You may use setup set

1

H 90° pulse and the 13C 90° pulse—the pulses must be equal. Adjust

dwell time. Set parameter sw1 to the value

1

dipof2 is set to 'y' to use a second decoupler offset during acquisition. dof determines

offset, which may be set above or below the 1H chemical shift region if a pedestal is

the f

1

present in f

. In this case, set dipoff for the center of the 1H shift region for best

1

decoupling. dipof2 is set to 'n' to use dof during the evolution period and decoupling.

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Chapter 6. Solid-Sta te NMR Experi ments

Reference

Bielecki, A.; Burum, D. P.; Rice, D. M.; Karasz, F . E. Macromolecules 1991, 24, 4820.

6.7 WISE1—Tw o-Dimensional Proton Wideline Separation

WISE1 correlates the CP/MAS spectrum of the observe nucleus with the proton wideline
spectrum due to
exchange experiment that mixes wideline patterns due to proton spin diffusion. The method
was first presented by Zumbulyadis for the study of amorphous silicon semiconductors.
The method was extended to polymers, and Schmidt-Rohr et al added a mixing period was.

WISE1 is useful for the characterization of polymers with complex morphology that
includes hard and soft domains. Domains are distinguished by the wideline spectrum, broad
if rigid and narrow if motionally averaged. Corresponding observe chemical shifts indicate
the segmental composition of the regions. With a spin diffusion mixing period WISE1
additionally determines proximity of the domains in space. WISE1 also provides the means
to obtain the proton wideline spectrum a UNITYplus system with only a standard digitizer .
For WISE1, sw1 can be set in excess of 100 kHz.

The macro wise1 conver ts a parameter set, obtained with XPOLAR or XPOLAR1, for the
WISE experiment. Power levels and proton 90
parameters set up for WISE with no mix period and a 200-kHz spectral width.

1H–1

H and X–1H interactions. An optional mixing period provides an

° pulse width are retained. Default

Applicability

WISE1 is a v ailab le fo r UNIT Yplus and
version 2.1.

UNITY

INOVA systems and can be found in SolidsLib

Parameters

WISE1 uses the UNITYplus parameters, tpwr, tpwrm, dpwr, cppwr, dipolr,
crossp, dblv12, pw and cntct (see page 85 for a description of these parameters).

mixflag='y' adds two 90° pulses that bracket a mixing period for proton spin diffusion.
mixflag='n' provides a proton pulse, evolution period, and cross polarization.

References

Zumbulyadis, N. Physical Review B 1986, 33, 6495.
Schmidt-Rohr, K.; Clauss, J.; Spiess, H. W. Macromolecules 1992, 25, 3273–3277

6.8 XPOLWFG1—Cross-Polarization with Programmed
Decoupling

XPOLWFG1 is a version of XPOLAR1 that provides for programmed decoupling during
acquisition using an optional waveform generator. Decoupler patterns are found in .DEC
files in the directory shapelib. In principle any decoupler pattern can be used, though it
should be noted that most “liquids” patterns, waltz, xy32, etc., are not necessarily useful
for solids. Several useful patterns are described below and are included in the shapelib
directory of SolidsLib , version 2.1.

93

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

6.8 XPOLWFG1—Cross-Polarization with Programmed Decoupling

XPOL WFG1 gates the w a veform generator on and off with a fastline (no AP bus delay) at
the beginning and end of the acquisition period if dm='nny' and dmm='ccp'. If
dm='c' the usual continuous wave decoupling is applied and as usual if dm='n' no
decoupling is applied.

XPOLWFG1 does not include p180, toss, pdp and pcrho at present.

Applicability

XPOLWFG1 is available for UNITYplus and
SolidsLib version 2.1.

UNITY

INOVA systems and can be found in

Macro

The macro xpolwfg1 converts a parameter set, obtained with XPOLAR or XPOLAR1,
for programmed decoupling. Po wer lev els and proton 90

° pulse width are retained. Default

parameters include dseq='tppm2' and dres=90. The value of dmf, the decoupler
modulation frequency, is estimated with the relation dmf= (dipolr/crossp) *(1/
4*pw). This value should be fine-tuned for optimum decoupling.

Parameters

xpolwfg1 uses the UNITYplus parameters, tpwr, tpwrm, dpwr, cppwr, crossp,
db1v12, pw and cntct (see page 85 for a description of these parameters).

dm is set to 'nny' to obtain decoupling.
dmm is set to 'ccp' to obtain programmed decoupling during acquisition and set to 'c'

for continuous decoupling. For dmm='c' the wfg parameters are hidden.
dmf is the decoupler modulation frequency and is set equal to one over four times the

decoupler 90°

° pulse. dmf must be calibrated and depends upon the value of dipolr. The

macro makes an estimate as describe d abov e. Calibrate dipolr with a sample of dioxane
and the macro h2cal or to fine tune, obtain spectra versus dmf and choose that with the
greatest narrowing.

dres is the waveform resolution, and it depends on the decoupler waveform.

Waveforms

Three waveforms are included in the shapelib of Solidslib 2.1. Fo r eac h wa v ef orm
name.DEC, set dseq='name'. Set dmf and dres according to the text in each
shapefile.

tppm2.DEC provides phase-modulated decoupling as presented by Bennett et al. For

crystalline materials—for example, glycine and linear polyethylene—PM decoupling
narrows the residual linewidth up to about 30% over CW decoupling. The pattern consists
of approximate
and the phase angle in the .DEC file for best decoupling at a particular field strength and
spinning speed.

π pulses with alternating phases of about ±10° to 30 degrees°. Vary dmf

blew 48.DEC provides decoupling with BLEW-48 according to Burum et. al. BLEW-48

13C–1

decouples protons from themselves but leaves a scaled

01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR

H dipolar interaction.

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Chapter 6. Solid-Sta te NMR Experi ments

fslg2.DEC provides phase continuous frequency switched Lee-Goldberg decoupling.

13C–1

This pattern decouples protons from themselves, but leaves a residual

H dipolar

interaction.

Reference

Bennett, A. E; Rienstra, C. M.; Auger, M.; Lakshmi, K. V.; Griffin, R. G. Poster 368.
36th Experimental Nuclear Magnetic Resonance Conference, 1995.

6.9 XPOLXMOD1—Wa veform Modulated Cross-P olarization

XPOLXMOD1 provides modulation of the X-channel of the Har tmann-Hahn match with a
selected waveform f ile. A second sequence, XPOLHMOD1, mo dulates the proton channel.
In general, modulated CP improves signal- to-noise and quantitation of CP/MAS spectra at
high spinning speeds. These two sequences provide access to a variety of the phase­frequency and amplitude-modulated CP methods in the literature.

Two macros xmodcos and xmodramp create specific amplitude modulated cosine and
ramped waveform (.DEC) files. This sequence requires a waveform generator on the
appropriate channel (X or H). Without a waveform generator, or for general purposes, use
VACP instead. Figure 38 is a diagram of the sequence.

cntct

(tpwrm)

xpolxmod1

Tx

Dec

"pattern"

pw

xpolhmod1

(pwpuls)

d1

AC

cntct

(crossp)

xpolhmod1

"pattern"

at

(dipolr)

Figure 38. XPOLXMOD1 Pulse Sequence

Applicability

XPOLXMOD1 and XPOLHMOD1 are available on UNITYplus and
present in userlib. One w av eform generator is required, and it can be placed on channel
1 or channel 2 as needed.

UNITY

INOVA and

95

Macros

The macros xpolxmod1 and xpolhmod1 convert a parameter set obtained with
XPOLAR or XPOLAR1 for these experiments Power levels and pulse widths are retained.

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

6.9 XPOLXMOD1—Waveform Modulated Cross-Polarization

For VNMR 5.1 and later crossp scales the proton waveform and tpwrm scales the X
waveform. The macros xmodramp and xmodcos create their respective .DEC files.
They also serve as a prototype for the creation of custom waveforms.

Parameters

XPOLXMOD1 and XPOLHMOD1make use of the UNITYplus and
parameters tpwr, tpwrm, dpwr, cppwr, dipolr, crossp, dblvl2, pw and cntct.
See page 85 for a description of these parameters. All other functions (i.e. toss, etc) of
XPOLAR1 are also present.

pattern is a string with the name of the .DEC file used for modulation.
pwpuls is the amplitude of the linear modulator during only the initial proton pulse of

XPOLHMOD1.
crossp is the amplitude of the proton linear modulator during cross polarization and this

value scales the waveform for XPOLHMOD1.
tpwrm is the amplitude of the X linear modulator during cross polarization and this value

scales the waveform for XPOLXMOD1.

UNITY

INOVA

Waveforms

Two macros are provided to ca lculate commo nl y us ed waveforms, a cosine function and a
ramp. For general wa veform s to be used for cros s polarizatio n, a duration of 1.0 in the f irst
column must be 0.2 microseconds. dmf and dres are not used to control the cross
polarization waveform. You can also set programmed decoupling during acquisition by the
usual procedure using dmf and dres.

xmodcos(frac,per,amp) creates a waveform with the following function:
amp*(1.0 - frac/2.0 + (frac/2.0)*cos(t/per))

where t is time. The resulting .DEC file has the form xmodcos_frac_per_amp.DEC
where frac is x10000 and per is in microseconds. The defaults are per=1/srate (the
value needed for reference 1) and amp=1023.

xmodramp(frac,per,amp) creates a waveform with the following function:
amp*(1.0 - frac/2.0 + (frac/2.0)*(1.0 - 4.0*t/per))

for 0.0 < t < per/2.0

and

amp*(1.0 - frac/2.0 + (frac/2.0)*(-1.0 + 4.0*t/per))

for per/2.0 < t < per
The resulting .DEC file has the form xmodramp_frac_per_amp.DEC where frac is

x10000 and per is in microseconds. The defaults are per=1/srate and amp=1023.
amp is the amplitude of the waveform, amp=1023. VNMR 5.1 and later soft ware pro vide

scaling of amp with the value of crossp or tpwrm. For earlier versions, set amp to its
fixed v alue during the pulse sequence ( <1023), where amp=1023 is a full amplitude of the
linear modulator.

frac is the fraction of modulated intensity, a value between 0 and 1.0.
per is the period of cosine modulation for 0 to 2

π radians. For a ramp, the slope is negativ e

(1-4t/per) for t=0 to per/2 and positive (1+4t/per) for t=per/2 to per. Set per
relative to cntct to obtain a specific shape or ramp during the contact time.

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Chapter 6. Solid-Sta te NMR Experi ments

References

Hediger, S.; Meier, B. H.; Ernst, R. R. Chem. Phys. Lett. 1993, 213, 627.

6.10 VACP—Variable Amplitude Cross-Polarization

As typical field strengths and rotor speeds used for CP/MAS increase, a problem that
develops is the rotor speed depend ence of cross-polarization. Usually signal-to-noise drops
and the zero-speed Hartmann-Hahn match splits into a set of sidebands.

A straight-forward solution is to vary the pulse amplitude during the contact time of the
cross-polarization. A set of alternating amplitudes with an increasing difference during the
contact time is quite effective in removing the spinning speed dependence of cross­polarization. In the VACP sequence, during the contact time,
levels with the appropriate amplitudes. The difference between the maximum and

γB

minimum values of

(in Hz) should be at least twice the maximum rotor speed to be

2

used. Figure 39 is a diagram of the VACP sequence.

cntct

(tpwrm)

1

H power is varied amo ng 11

Tx

Dec

cntct

pw

d1

AC

(vacp[11])

at

(dipolr)

Figure 39. VACP Pulse Sequence

Applicability

VACP is available on

UNITY

INOVA, UNITYplus, and UNITY. It is found in userlib.

Macro

The vacp macro sets up parameters for the VACP pulse sequence an d can take two or three
arguments. vacp sets default levels for the arrayed parameter vacp. Units are the same as
crossp. vacp[0]=crossp, vacp[n]–vacp[n–1]=500, and n=11. Syntax is as
follows: vacp<(<<<vacp[n]–vacp[n–1],vacp[0]>,n>)>. The vacplist
macro lists VACP levels and resets array='' (two single quotes).

97

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

6.11 XPOLEDIT1—Solids Spectral Editin g

Parameters

VACP uses the

dipolr, dblvl2, pw, and cntct. See page 85 for a description of these parameters.
vacp is an array of linear modulator settings to be used during cross-polarization. After

vacp is set, set array=''. The command da is inoperative when array=''. Use the
vacplist macro instead to display the vacp array.

UNITY

INOV A and UNITYplus parameters tpwr, tpwrm, dpwr, cppwr,

Reference

Peersen, O.; Wu, X.; Kustanovich, I.; Smith, S. O. J. Magn. Reson. 1993, 104 (Series
A), 334.

6.11 XPOLEDIT1—Solids Spectral Editing

XPOLEDIT1 provides for spectral editing of CH3, CH2, CH and C carbons by use of
differences in their cross polarization properties. The s equence provides a 180
during the contact time (depolarization) followed by a return to the original phase
(repolarization). Individual carbo n types can be nulled with appropr iate delays p3 and p4
and spectral editing can be achieved by addition and subtraction of subspectra obtained
with the different delays. Figure 40 is a diagram of the XPOLEDIT1 sequence.

° phase shift

(tpwrm)

Tx

pw

(crossp)

d1

Dec

AC

Applicability

XPOLEDIT1 is available on

cntct

cntct

p3

p3

p4

p4

Figure 40. XPOLDIT1 Pulse Sequence

UNITY

INOVA and UNITYplus and present in userlib.

at

(dipolr)

Macro

The macro xpoledit1 converts a parameter set obtained with XPOLAR or XPOLAR1
for XPOLEDIT1. Power levels and pulse widths are retained.

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Chapter 6. Solid-Sta te NMR Experi ments

Parameters

XPOLEDIT1 makes use of the
dpwr, cppwr, dipolr, crossp, dblvl2, pw and cntct. See page 85 for a
description of these parameters.

p3 is the depolarization time, in microseconds. The phase of the proton channel is reversed.
p4 is the repolarization time, in microseconds.

UNITY

INOV A and UNITYplus parameters tpwr, tpwrm,

References

Sangil, R.; Bildsoe, H.; Jacobsen, H. J. J. Magn. Reson. 1994, 107 (Series A), 67.

6.12 3QMAS1—Triple-Quantum 2D for Quadrupole Nuclei

3QMAS1 is a two-pulse, two-dimensional experiment for the detection of isotropic spectra
of quadrupole nuclei (I=n/2, n/2>1/2) in the solid state (an optional third selective
refocusing pulse may also be present). Isotropic spectra o f quadrupole nuclei are produ ced
in the f1 dimension. The resonance frequencies are determined by both the chemical shift
and the quadrupole interaction and are field dependent.

The lineshape in the f2 dimension is similar to that obtained with MAS alone. Because
resonances are resolved in f1 the lineshapes are easily simulated individually with a general
simulation program such as STARS. The shift in f1 and the lineshape in f2 are related and
provide redu ndant infor mation about quadrupole and chemical shift tensor components.

Figure 41 is a diagram of the 3QMAS1 sequence.

pw3q pw3q

pws

d1 d2 tau

periods/srate

AC

(tpwrms)

at

Figure 41. 3QMAS1 Pulse Sequence

The pulse sequence and phase cycle are based on work don e by D. Massiot et al and were
first provided by J. Stebbins of Stanford University. We thank the authors for the
opportunity to view their work before publication.

99

Applicability

3QMAS1 is available for all UNITY systems and can be found in the userlib. The
default parameters of the setup macro are applicable for only
The processing parameter daslp is present in VNMR 5.2 and later.

The 3QMAS1 experiment requires only MAS hardware and in many circumstances this
method can replace the need to do the more complicated experiments, double rotation

VNMR 6.1C User Guide: Solid-State NMR 01-999162-0 0 C0402

UNITY

INOV A and UNITYplus.

6.12 3QMAS1—Triple-Quantum 2D for Quadrupole Nuclei

(DOR) and dynamic angle spinning (DAS). 3QMAS1 is a robust experiment that is well
worth trying before contemplating the use of DOR or DAS.

Macro

The macro s3qmas1 converts a parameter set for the triple -qu antum MAS experiment
3QMAS1. pw3q is set to 180
excite triple quantum coherence) with the assumption that pw is the 90

° pulse length (the minimum practical p ulse length needed to

° pulse length. If

tpwrm is not present (as in many older parameter sets), 3qmas1 creates it and sets it to
the value of tpwrf. If tpwrf is not present, tpwrm is set to 4095. The default is
pws=0.0 for no refocusing pulse and sw1=sw. The macro s3qmas1 creates the
processing parameter daslp used for shearing (applicable for VNMR 5.2 or greater).

Parameters

3QMAS1 makes use of the
dpwrm and pw. See page 117 for a description of these parameters.

UNITY

INOV A and UNITYplus parameters tpwr, tpwrm, dpwr,

pw is the observe 90
nucleus. The macro s3qmas1 uses pw to calculate the default 180

° pulse, in microseconds, for a solution-state sample of the quadrupole

° pulse. pw is not used

in the pulse-sequence.
pw3q is the length of pulses 1 and 2 of 3QMAS1. It is used to generate triple quantum

coherence (pulse 1) and then return it to single quantum coherence (p ul se 2) for detection.
The default is pw3q=2*pw. Set pw3q to a larger value (e.g., pw3q=8*pw) for greater
triple-quantum signal-to-noise in some cases.

tpwr is the observe coarse-attenuator setting for pulses 1 and 2.
tpwrm is the observe linear-modulator setting for pulses 1 and 2.
tpwrs is the observe coarse-attenuator setting for the selective refocusing pulse (pulse 3).

The default is tpwrs=tpwr.
tpwrms is the observe linear-mo dulator setting for the selective refo cusing pulse (pulse 3).

The default is tpwrms=tpwrm/5, but this pulse must be calibrated.
pws is the length of the optional selective refocusing pulse (pulse 3). The default is

pws=0.0 and the refocusing pulse is absent. For refocusing, set pws=10*pw for the
default value of tpwrms=tpwrm/5.

srate must be set to the actual rotor speed. This value is used with periods to calculate
the delay, tau, before the refocusing pulse.

periods is the number of rotor periods before the selective refocusing pulse. This delay
is present only if pws>0.0 and by default it is absent.

daslp is a processing parameter required to shear the triple-quantum 2D dataset and rotate
the narrow axis of each correlation to the f1 dimension. Set daslp<0.0 for I=3/2 and
daslp>0.0 for I=5/2. daslp is av ailable for VNMR v ersion 5.2 and later (refer to the

VNMR Command and Par ameter Reference).

phase=1,2 are the sine and cosine components of hypercomplex Fourier transform,
wft2da.

References

Frydman, L.; Harwood, J. S. J. Am. Chem. Soc. 1995, 117, 5367.

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100