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Solid-State NMR
User Manual
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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
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.
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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
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