JEOL JNM-ECA Series User manual

JNM
-
ECA Series
JNM-ECX Series
(Delta V5.0)
SOLID
MEASUREMENT
USER’S MANUAL
For the proper use of the instrument, be sure to
read this instruction manual. Even after you
read it, please keep the manual on hand so that
you can consult it whenever necessary.
INMECAXS_V50-SLD-2
FEB2010-08110273
Printed in Japan
INSTRUCTIONS

JNM-ECA Series
JNM-ECX Series
(Delta V5.0)
SOLID
MEASUREMENT
USER’S MANUAL
JNM-ECA Series JNM-ECX Series
In the ECA or ECX NMR instrument, solid-state NMR measurement becomes
possible when you add optional attachment, such as solid probe, to the
standard composition.
This manual explains about cautions, measurement conditions, processing
conditions, multi-nuclear measurement, relaxation-time measurement, and
pulse sequence used in the solid experiment when solid NMR measurement
will be carried out in JNM-ECA/ECX series.
Please be sure to read this instruction manual carefully,
and fully understand its contents prior to the operation
or maintenance for the proper use of the instrument.

NOTICE
• This instrument generates, uses, and can radiate the energy of radio frequency and, if not installed and used in
accordance with the instruction manual, may cause harmful interference to the environment, especially radio
communications.
• The following actions must be avoided without prior written permission from JEOL Ltd. or its subsidiary company
responsible for the subject (hereinafter referred to as "JEOL"): modifying the instrument; attaching products other than
those supplied by JEOL; repairing the instrument, components and parts that have failed, such as replacing pipes in the
cooling water system, without consulting your JEOL service office; and adjusting the specified parts that only field
service technicians employed or authorized by JEOL are allowed to adjust, such as bolts or regulators which need to be
tightened with appropriate torque. Doing any of the above might result in instrument failure and/or a serious accident. If
any such modification, attachment, replacement or adjustment is made, all the stipulated warranties and preventative
maintenances and/or services contracted by JEOL or its affiliated company or authorized representative will be void.
• Replacement parts for maintenance of the instrument functionality and performance are retained and available for seven
years from the date of installation. Thereafter, some of those parts may be available for a certain period of time, and in
this case, an extra service charge may be applied for servicing with those parts. Please contact your JEOL service office
for details before the period of retention has passed.
• In order to ensure safety in the use of this instrument, the customer is advised to attend to daily maintenance and
inspection. In addition, JEOL strongly recommends that the customer have the instrument thoroughly checked up by
field service technicians employed or authorized by JEOL, on the occasion of replacement of expendable parts, or at the
proper time and interval for preventative maintenance of the instrument. Please note that JEOL will not be held
responsible for any instrument failure and/or serious accident occurred with the instrument inappropriately controlled or
managed for the maintenance.
• After installation or delivery of the instrument, if the instrument is required for the relocation whether it is within the
facility, transportation, resale whether it is involved with the relocation, or disposition, please be sure to contact your
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authorized by JEOL, JEOL will not be held responsible for any loss, damage, accident or problem with the instrument.
Operating the improperly installed instrument might cause accidents such as water leakage, fire, and electric shock.
• The information described in this manual, and the specifications and contents of the software described in this manual
are subject to change without prior notice due to the ongoing improvements made in the instrument.
• Every effort has been made to ensure that the contents of this instruction manual provide all necessary information on
the basic operation of the instrument and are correct. However, if you find any missing information or errors on the
information described in this manual, please advise it to your JEOL service office.
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• This manual and the software described in this manual are copyrighted, all rights reserved by JEOL and/or third-party
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©Copyright 2009,2010 JEOL Ltd.
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Foreign Trade Control Law” of Japan in compliance with international security export control. If you intend to export
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MANUFACTURER
JEOL Ltd. 1-2, Musashino 3-chome, Akishima, Tokyo 196-8558 Japan
Telephone: [phone] Facsimile: 81-42-546-3353 URL: http://www.jeol.co.jp/
Note: For servicing and inquiries, please contact your JEOL service office.

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If you do not agree to the terms and conditions of the Agreement, please do not use the software and contact JEOL Ltd.
Software License Agreement
This Software License Agreement is made and entered into by and between you, the end-user customer, and JEOL Ltd.
(hereinafter referred to as JEOL) in witness of agreement between both parties upon licensing of the right to use the
software (which is hereinafter referred to as the Licensed Software) owned by JEOL.
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not disclose the Licensed Software to any third party.
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NOTATIONAL CONVENTIONS AND GLOSSARY
■ Examples for general notations
— CAUTION — : Important precautions for use, which, if not followed, may result in
damage to or problems with the device itself.
": Additional points to remember regarding the operation.
): A reference to another section, chapter or manual.
1, 2, 3: Numbers indicate a series of operations that achieve a task.
◆: A diamond indicates a single operation that achieves a task.
File: The names of menus, commands, or parameters displayed on the
screen are denoted with bold letters.
File–Exit : Selecting a menu item from a pulldown menu is denoted by linking
the menu and the item with a dash (–).
For example, File–Exit means selecting Exit from the File menu.
Ctrl : Keys on the keyboard are denoted by enclosing their names in a
box.
■ Examples for mouse terminology
Mouse pointer: A mark, displayed on the screen, which moves following the
movement of the mouse. It is used to specify a menu item, com-
mand, parameter value, and other items. Its shape changes accord-
ing to the situation.
Click: To press and release the left mouse button.
Right-click: To press and release the right mouse button.
Double-click: To press and release the left mouse button twice quickly.
Drag: To hold down the left mouse button while moving the mouse.
N-1

CONTENTS
SAFETY PRECAUTIONS
PRECAUTIONS FOR USE
1. OUTLINE OF SOLID-STATE NMR MEASUREMENT
1.1 SOLID-STATE NMR SYSTEM ............................................................1-1
1.2 DIFFERENCE BETWEEN SOLID-STATE NMR AND
SOLUTION NMR..................................................................................1-2
2. FUNDAMENTALS OF SOLID-STATE NMR MEASUREMENT
2.1 INTERACTIONS INFLUENCING SOLID-STATE NMR
SPECTRUM...........................................................................................2-1
2.2 MAGIC ANGLE SPINNING.................................................................2-2
2.3 HIGH POWER DECOUPLING.............................................................2-3
2.3.1 CW (Continuous Wave) Decoupling ..............................................2-3
2.3.2 TPPM (Two Pulse Phase Modulation) Decoupling ........................2-3
2.4 SINGLE PULSE MEASUREMENT .....................................................2-4
2.5 CROSS POLARIZATION .....................................................................2-5
2.5.1 Principle of Cross Polarization........................................................2-5
2.5.2 Notes of Cross Polarization.............................................................2-6
3. SETTING OF INSTRUMENT CONDITIONS
3.1 PRECAUTION FOR OPERATION .......................................................3-1
3.2 ADJUSTMENT OF MAGIC ANGLE ...................................................3-3
3.3 SETTING OF IRRADIATION FREQUENCY......................................3-4
3.4 SETTING PULSE WIDTH....................................................................3-5
3.5 ADJUSTMENT OF RESOLUTION......................................................3-7
3.6 REFERENCE SETTING .......................................................................3-8
3.6.1 External Reference Setting..............................................................3-8
3.6.2 Reference Setting by Using Z0 Shim..............................................3-9
3.7 ADJUSTMENT OF CROSS-POLARIZATION CONDITIONS.........3-10
3.7.1 Adjustment of Cross-Polarization Condition under Low-speed
Spinning ........................................................................................3-10
3.7.2 Adjustment of CP Condition under High Speed Spinning............3-11
3.7.3 Adjustment of VACP Conditions..................................................3-11
3.7.4 Selecting a Method for Cross Polarization....................................3-12
3.8 ADJUSTMENT OF DECOUPLING CONDITIONS..........................3-13
3.8.1 Setting of CW (Continuous Wave) Decoupling Conditions .........3-13
3.8.2 Setting of TPPM Decoupling Conditions......................................3-13
3.8.3 Setting of XiX Decoupling Conditions .........................................3-14
3.8.4 Setting of SPINAL64 Decoupling Conditions ..............................3-14
3.8.5 Setting of CM Decoupling Conditions..........................................3-15
3.8.6 Setting of SWf-TPPM Decoupling Conditions .............................3-15
NMECAXS_V50-SLD-2 C-1

CONTENTS
4. ADJUSTMENT OF MEASUREMENT CONDITIONS AND
PROCESSING CONDITIONS
4.1 SETTING PULSE WIDTH IN SINGLE PULSE
MEASUREMENT..................................................................................4-1
4.2 SETTING WAITING TIME IN SINGLE PULSE
MEASUREMENT..................................................................................4-2
4.3 SETTING CONTACT TIME IN CP METHOD ....................................4-3
4.4 SETTING WAITING TIME IN CP METHOD .....................................4-4
4.5 SETTING SAMPLING POINT (X_POINTS).......................................4-5
4.6 HOW TO USE FORWARD LINEAR PREDICTION ...........................4-6
4.7 HOW TO USE BACKWARD LINEAR PREDICTION........................4-7
5. MULTINUCLEAR MEASUREMENT
5.1 OUTLINE OF MULTINUCLEAR MEASUREMENT..........................5-1
5.2 METHOD OF MEASURING RARE SPIN NUCLEUS OF SPIN
1/2 ...........................................................................................................5-2
5.3 METHOD OF MEASURING 1H/19F......................................................5-2
5.4 METHOD OF MEASURING NUCLEUS OF SPIN 1 ..........................5-3
5.5 METHOD OF MEASURING NUCLEUS OF HALF-INTEGER
SPIN........................................................................................................5-3
6. MEASUREMENT OF RELAXATION TIME
6.1 OUTLINE OF RELAXATION-TIME MEASUREMENT.....................6-1
6.2 RELAXATION TIME MEASUREMENT BY DIRECT
MEASUREMENT..................................................................................6-2
6.3 RELAXATION TIME MEASUREMENT OF 13C BY TORCHIA
METHOD ...............................................................................................6-4
6.4 MEASUREMENT OF T1ρ(T1IN THE ROTATING FRAME) .............6-5
6.5 RELAXATION TIME MEASUREMENT OF 1H BY INDIRECT
OBSERVATION USING CP METHOD ................................................6-6
7. MQMAS METHOD
7.1 OUTLINE OF MQMAS METHOD.......................................................7-1
7.2 PRINCIPLE ............................................................................................7-3
7.3 ADJUSTMENT ......................................................................................7-5
7.3.1 Adjustment of Power .......................................................................7-5
7.3.2 Adjustment of Parameters ...............................................................7-6
7.4 MEASUREMENT..................................................................................7-8
7.5 PROCESSING........................................................................................7-9
7.6 APPENDIX ..........................................................................................7-12
7.6.1 Shearing process............................................................................7-12
7.6.2 Scaling Processing.........................................................................7-13
INDEX
C-2 NMECAXS_V50-SLD-2

SAFETY PRECAUTIONS
Although this instrument is protected with safety device which prevents the occurrence of accident
that could result in an injury, harm, and damage to the users or instrument itself, the safety feature
may not work properly if you use the instrument for the purpose of use not intended or in an im-
proper usage. For the proper use of the instrument, please be sure to read all of the instructions,
descriptions, notices, and precautions contained in this manual carefully to understand them fully
prior to the operation or maintenance. This section, “Safety Precautions,” contains important in-
formation related to safety for using of the instrument.
The safety indications and their meanings are as follows:
DANGER: An imminently hazardous situation which, if not avoided, will result in death
or serious injury.
WARNING: A potentially hazardous situation which, if not avoided, could result in death
or serious injury.
CAUTION: A potentially hazardous situation which, if not avoided, may result in minor
or moderate injury, or a situation that could result in serious damage to fa-
cilities or acquired data.
Labels bearing the following symbols are attached to dangerous locations on the instrument. Do not
touch any of these locations with your hands or anything else.
Beware of
electric shock Beware of laser
Beware of
super low temp Beware of getting caught Beware of biohazard Do not
disassemble
Beware of
heat
Examples of symbols
• Use the instrument properly within the scope of the purpose and usage
described in its brochures and manuals.
• Never open/remove protective parts (exterior panels) and parts that can't
be opened/removed without use of tool (including key), or disconnect/
connect the cables/connectors that are not described in this manual.
• Never attempt to do any works of disassembling/assembling the instru-
ment other than those described in this manual.
• Never make modifications that include installing substitute parts and
disabling safety devices or other safety features.
• Never disconnect the grounding wire or move it from the prescribed posi-
tion. Failure to follow this instruction could result in electric shock.
• To avoid falling, do not climb onto the operation table and console during
daily operation or during maintenance or inspection.
• When you dispose of the instrument or liquid or other waste, follow all
applicable laws and regulations, and dispose of it in a proper manner
without polluting the environment.
• Be sure to read the “Safety Precautions” section of the manuals for the
accessories attached to or built into the instrument.
• If anything is unclear, please contact your JEOL service office.
NMECAXS_V50-SLD-2 S-1

SAFETY PRECAUTIONS
WARNING for Installation
• Do not attempt to install the instruments by yourself.
Installation work requires professional expertise and JEOL is responsible for the in-
stallation of the instruments and related attachments purchased from JEOL.
Consult your JEOL service office.
WARNING
• When you use nitrogen gas, provide ventilation sufficient for the rate of
gas usage.
When ventilation is insufficient, the danger of asphyxiation will be present. Moreover,
when using nitrogen gas, in order to avoid unexpected accidents, be sure to provide an
oxygen alarm.
S-2 NMECAXS_V50-SLD-2

PRECAUTIONS FOR USE
Important precautions, which, if not followed, may result in damage to the device itself,
are described below.
• The probe may become damaged if the data-acquisition time is too long.
• Liquid samples, samples whose volume changes (such as between the
solid and liquid states) when due to a change in temperature, and
sublimating materials cannot be measured.
Scattering the sample or bolts for the spinning cap occurs due to a change in volume
caused by the expansion of the sample. Both of these events destroy the probe.
• When you perform VT (Variable Temperature) measurement, be sure to
flow bearing gas.
If you do not flow the bearing gas, the heater produces anomalous heating then a fire
might occur inside the probe.
• When you set the measurement temperature to 150 ℃or more, be sure
to use nitrogen gas.
If air is used, a flammable sample may ignite and fires might occur inside the probe.
Moreover, the surface of the heater that is built into the probe would oxidize and the
oxide would block a pipe, causing failure. The NMR detection coil would also
oxidize and performance of the probe would deteriorate.
• Carefully read the instruction manual then perform the magic angle
spinning.
There is a danger of destroying the probe.
• When you first adjust the magic angle, receive instructions from an
experienced person.
An incorrect adjustment might damage the probe.
NMECAXS_V50-SLD-2 P-1

1
OUTLINE OF SOLID-STATE
NMR MEASUREMENT
1.1 SOLID-STATE NMR SYSTEM ........................................................................ 1-1
1.2 DIFFERENCE BETWEEN SOLID-STATE NMR AND SOLUTION
NMR................................................................................................................... 1-2
NMECAXS_V50-SLD-2

1 OUTLINE OF SOLID-STATE NMR MEASUREMENT
NMECAXS_V50-SLD-2 1-1
1.1 SOLID-STATE NMR SYSTEM
High-Resolution solid-state NMR measurement by techniques such as cross-polarization
magic-angle spinning (CPMAS) method becomes possible when you add optional at-
tachments (such as a probe for the solid-state measurement) to the standard composition
of JNM-ECA/ECX series. Moreover, multinuclear observation and the measurement un-
der variable temperatures (VT) are also possible with this system.
If the Status cable is connected to the Status connector of the solid probe, the program
and the spectrometer will enter the solid mode automatically. The instrument is in the
solid mode if the LIQUID lamp of the INT CONT unit located behind the door on the
right of the front of the spectrometer is turned off.
LIQUID lamp
Fig. 1.1 INT CONT unit
The procedure for the measurement and processing in the solid mode are the same as
those for the solution mode. In this manual, measuring methods peculiar to the solid-state
NMR will be explained.

1 OUTLINE OF SOLID-STATE NMR MEASUREMENT
1.2 DIFFERENCE BETWEEN SOLID-STATE NMR AND
SOLUTION NMR
The feature of solid high-resolution NMR that makes it different from solution NMR is
the ability to measure a solid sample as it is. In solution NMR, since an observed mole-
cule is dissolved in a solvent, almost all magnetic interactions except the spin-spin inter-
action can be eliminated by rapid molecular motion. Although the chemical bond struc-
ture of the molecule can be analyzed in detail by using high-resolution spectra in solution
NMR, since it is dissolved in the solvent, the special features of the solid state will be lost.
On the other hand, in solid-state NMR, the sample can be observed as it is.
However, analysis of the spectrum becomes difficult in solid-state NMR since the signal
becomes broad due to the influence of various magnetic interactions ()Sect. 2.1),
which have disappeared in solution NMR.
Usually, in solid-state NMR, in order to make a signal with a narrow line and to improve
the signal-to-noise ratio, the measurement combines the following three methods.
a. High-speed magic angle spinning
b. High-power 1H decoupling
c. X-H cross polarization
Techniques aand bare methods for narrowing the line of a signal. Moreover, c is a
method of improving the signal-to-noise ratio. Chapter 2 explains these techniques.
1-2 NMECAXS_V50-SLD-2

2
FUNDAMENTALS OF
SOLID-STATE
NMR MEASUREMENT
2.1 INTERACTIONS INFLUENCING SOLID-STATE NMR SPECTRUM.......... 2-1
2.2 MAGIC ANGLE SPINNING............................................................................. 2-2
2.3 HIGH POWER DECOUPLING......................................................................... 2-3
2.3.1 CW (Continuous Wave) Decoupling.......................................................... 2-3
2.3.2 TPPM (Two Pulse Phase Modulation) Decoupling ................................... 2-3
2.4 SINGLE PULSE MEASUREMENT ................................................................. 2-4
2.5 CROSS POLARIZATION.................................................................................. 2-5
2.5.1 Principle of Cross Polarization................................................................... 2-5
2.5.2 Notes of Cross Polarization........................................................................ 2-6
NMECAXS_V50-SLD-2

2 FUNDAMENTALS OF SOLID-STATE NMR MEASUREMENT
NMECAXS_V50-SLD-2 2-1
2.1 INTERACTIONS INFLUENCING SOLID-STATE NMR
SPECTRUM
Usually, the interactions in the NMR are expressed as the sum of the seven interactions
shown below.
H = HZ+Hσ+HJ+HCSA+HJA+HD+HQ
HZ: Zeeman interaction
Hσ: Chemical shift isotropy
HJ: Spin-spin interaction (J coupling) isotropy
HCSA: Chemical shift anisotropy
HJA: Spin-spin interaction anisotropy
HD: Magnetic dipole-dipole interaction
HQ: Quadrupole interaction
HZis the main interaction that determines the fundamental resonance frequency of the
nucleus, and other interactions are expressed as perturbations of HZ. On a spectrum, you
can observe the perturbation terms. In the six perturbation terms, Hσ and HJare called iso-
tropic terms, and HCSA, HJA, HD, and HQare called anisotropic terms. The difference be-
tween anisotropic and isotropic terms is whether the interaction is dependent on the direc-
tion of the molecule or not.
Although anisotropic terms change greatly depending on the orientation of the molecule,
they become 0 (zero) if the orientation of the molecule is changed uniformly and aver-
aged. If the molecule is carrying out rotational Brownian motion, the anisotropic terms
disappear and only the isotropic terms remain.
Spectroscopy of solution NMR is constructed under the assumption that the averaging is
carried out by such molecular motion. However, in the solution NMR method, since ani-
sotropic terms may affect a relaxation phenomenon, and anisotropic terms may appear in
a spectrum by partial orientation of molecules in high-magnetic-field NMR, we cannot
ignore it completely.
On the other hand, in solid NMR that treats a solid sample that has no molecular motion
or is constructed from small molecules, anisotropic terms become rather dominant terms
in the interaction.
How to deal with these anisotropic terms is the main subject of solid-state NMR.
Usually, in solid-state NMR, interactions are eliminated by the following two methods.
a. Magic angle spinning(MAS)
b. High-power decoupling
By using these techniques, HCSA can be eliminated by magic angle spinning, and HDcan
be eliminated by magic angle spinning and high-power decoupling. Moreover, HQexists
only in a nucleus whose nuclear spin is larger than one half, and can be eliminated by the
MQMAS (Multiple Quantum-Magic Angle Spinning) method ()Chap. 7).
Since HJA can hardly be observed, we usually ignore it.

2 FUNDAMENTALS OF SOLID-STATE NMR MEASUREMENT
2.2 MAGIC ANGLE SPINNING
Magic Angle Spinning (MAS) is a spinning technique in which the sample rotates on an
axis at 54.74 degree (= arccos 3/1 ) with respect to the static magnetic field. MAS is the
most fundamental and important technique in the solid-state NMR.
Rotating axis
Sample tube
54.74°ν
r
B0
Fig. 2.1 Magic Angle Sample Spinning
MAS can eliminate all the anisotropic interactions expressed as second-rank tensors (HD,
HCSA, HQ). However, when the MAS frequency is smaller than the interaction, the interac-
tion remains partially or the effect of MAS is not expressed fully. The partially remaining
interaction appears as spinning sidebands or as a broadening of a main peak. Generally,
since the HDwith 1H cannot be completely eliminated by only using MAS, high-power
decoupling ()Sect. 2.3) is used together with MAS.
2-2 NMECAXS_V50-SLD-2

2 FUNDAMENTALS OF SOLID-STATE NMR MEASUREMENT
2.3 HIGH POWER DECOUPLING
When 1H and 13C are directly coupled, the dipole interaction with 1H is about 20 kHz. In
order to completely eliminate the dipole interaction with the 1H, 1H high-power decoup-
ling of about 60-80 kHz is usually required. Since there is a strong dipole interaction be-
tween the protons in an organic compound, you cannot use the technique of broad-band
decoupling that is used in the solution NMR. Therefore, it is necessary to decouple with
the high-power RF pulse. High-power decoupling peculiar to the solid-state NMR is
called “Dipolar Decoupling.”
Since RF pulses used for the high-power decoupling are very strong, decoupling is car-
ried out only during data acquisition.
CAUTION
The probe may become damaged if the data-acquisition time is too long.
2.3.1 CW (Continuous Wave) Decoupling
The CW decoupling is a technique that has been used for many years. In solution NMR,
various decoupling sequences other than CW decoupling have been proposed. However,
the decoupling sequence of solution NMR has not demonstrated an effect in solid
high-resolution NMR for the following two reasons.
• Since there is a strong homonuclear dipole interaction between the 1H’s in a solid sam-
ple, a powerful artifact signal appears as a cycling sideband.
• In a pulse sequence having a long cycle, the decoupling effect is decreased by inter-
ference with MAS.
Moreover, CW decoupling has been a reliable decoupling technique because it is not in-
fluenced by imperfections in pulses.
2.3.2 TPPM (Two Pulse Phase Modulation) Decoupling
TPPM is a decoupling sequence proposed by A.E.Bennett et al.
Reference: A.E. Bennett et al., J.Chem.Phys., 103, 6951-6958 (1995).
Although it is a very simple decoupling sequence that repeats two 180°pulses in which
the phase only changed a small amount, the line-narrowing effect demonstrated in het-
eronuclear 1H decoupling is more than in CW decoupling.
TPPM decoupling is not for canceling the wide range off-resonance effect by using
weaker power like the decoupling sequence seen in solution NMR. Rather the decoupling
effect becomes better with increasing decoupling power. Therefore, when TPPM decoup-
ling is carried out, it uses the maximum decoupling power that can be used with the in-
strument the same as in CW decoupling.
The effect of TPPM decoupling depends on the flip angle ϕof the phase and the pulse
width τp. The TPPM decoupling with certain parameters cannot demonstrate an effect in
comparison with CW decoupling. Moreover, since the decoupling effect depends on the
pulse width, the effect decreases in a probe with poor uniformity of the RF magnetic field.
In TPPM decoupling, the decoupling effect will decrease if the power is weaker.
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2 FUNDAMENTALS OF SOLID-STATE NMR MEASUREMENT
In addition, since TPPM decoupling also decreases the interference between MAS speed
and CW decoupling, it also prevents the line-width from increasing under high-speed
MAS.
TPPM decoupling is especially effective in the following cases.
• High magnetic field (500 MHz or more)
• High-speed spinning
• 19F decoupling
• System that has heteronuclear interactions other than 1H such as 15N or 14N
2.4 SINGLE PULSE MEASUREMENT
One of the fundamental measuring methods of a solid-state NMR measurement is a sin-
gle-pulse measurement. When you carry out a single-pulse measurement, you use MAS.
Usually, although the cross-polarization method ()Sect. 2.5) is used in the solid-state
NMR of an organic compound, the single-pulse measurement is used for a sample which
does not contain the 1H nucleus or contains very few. Moreover, single-pulse measure-
ment may also be used for a sample with rapid molecular motion like adamantane. When
measuring a sample containing the 1H nucleus, high-power decoupling is used in addition
to MAS.
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2 FUNDAMENTALS OF SOLID-STATE NMR MEASUREMENT
2.5 CROSS POLARIZATION
The Cross-Polarization (CP) method is the technique most generally used in solid-state
NMR. The CP method is usually called the “CPMAS” method because it is used in com-
bination with MAS.
Usually, CPMAS measurement has the following advantage when comparing it with the
single-pulse measurement.
• Improvement of the SN ratio
• Shortening of repetition time (improvement in accumulation efficiency)
2.5.1 Principle of Cross Polarization
The 1H nucleus and X nucleus are irradiated by RF simultaneously, and the spin lock is
applied. The spin lock is a technique that irradiates a specific nucleus with a high-power
radio frequency at the resonance frequency to arrange the magnetization of the nucleus in
the direction of the B1magnetic field. When the B1magnetic field strengths of the
spin-lock frequency of these two nuclei become equal, exchange between the magnetiza-
tions happens. This is called the “Hartmann-Hahn conditions.” If we denote the B1mag-
netic field strengths for I and S nucleus as B1Iand B1Sand γratio of I and S nucleus as γI
and γS, respectively, the Hartmann-Hahn conditions can be expressed with the following
formula.
| γI B1I | = | γSB1S |
Be aware of the direction of the spin lock and magnetization when the magnetization of
the I and S nuclei reach equilibrium. When the signs of the γratio are the same, both
magnetizations are turned in the same direction. When the signs of the γratio are opposite,
the magnetizations are turned in opposite directions. For example, when observing the
magnetization transfer from 1H, the magnetizations of 13C (γratio is positive) and 29Si (γ
ratio is negative) are observed in reverse phase.
ZZ
B0
M I MS
B1IB1S
|γIB1I |＝|γSB1S |
or
Fig. 2.2 Cross polarization of I and S nuclei
This method is often used for the magnetization transfer from 1H to 13C. Using this
method improves the sensitivity of 13C by γ1H/γ13C= 4 times. Furthermore, since a meas-
urement can be repeated with approximately the relaxation time T1of 1H, accumulation
efficiency improves markedly.
)( 1
1
13
1HC TT .The improvement of accumulation efficiency is
This method is applied for the rare spin system (15N, 13C, 29Si and 31P) of the spins 1/2
containing 1H.
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