3 SETTING OF INSTRUMENT CONDITIONS
3.7 ADJUSTMENT OF CROSS-POLARIZATION CONDI-
TIONS
Adjustment of CP
（
Cross-Polarization
）
conditions is performed to satisfy the Hart-
mann-Hahn conditions. The Hartmann-Hahn conditions are different between low- speed
spinning and high-speed spinning. Therefore, you need to adjust the conditions according
to the spinning speed.
In this section, adjustment of CP conditions is explained for a spin 1/2 nucleus.
3.7.1 Adjustment of Cross-Polarization Condition under
Low-speed Spinning
The Hartmann-Hahn condition under low-speed spinning is the following equation.
γ
I
B
I
=
γ
S
B
S
Under actual work conditions, set the values of
irr_amp_cp
and
obs_amp_cp
so that the
90
°
pulse width for the observation nucleus equals the 90
°
pulse width for the irradiation
nucleus.
1.
Set the standard sample (such as, adamantane).
2.
Perform spinning at 5 kHz.
3.
Load the pulse sequence
cpmas.jxp
into
Experiment Tool
.
4.
Set
scans
to a multiple of 2.
5.
Set
obs_shape_cp
to
constant_cp
.
6.
Set
irr_amp_cp
value of
Proton
.
7.
Set the array measurement for
obs_amp_cp
of
Carbon13
.
8.
Click the
Submit
button.
The pulses occur, and the measurement starts.
If the measurement ends, the
nD Processor
window automatically opens.
9.
Perform the data processing.
Refer to the user’s manual “Data processing” for processing the data obtained
by the array measurement.
After data processing, the result is displayed by selecting
Linearize
.
10.
Examine the optimum
obs_amp_cp
value.
In the spectra for which you carried out the
Linearize
processing, the value of
obs_amp_cp
with the strongest signal intensity is the optimum value for
cross-polarization conditions.
Under high-speed spinning, two or more
obs_amp_cp
with strong signal intensities
exist. In this case, refer to the adjustment of CP conditions under high-speed spin-
ning (
Section 3.7.2).
3-10
NMECAXS_V50-SLD-2
