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7.3
ADJUSTMENT
Here the 3QMAS with the Z filter measurement is explained as an example because it is
most commonly used.
7.3.1
Adjustment of Power
Two power levels are used in the MQMAS measurement with the Z filter. They are the
high output power level used to excite the multiple-quantum coherence and the power
level for the selective excitation of the Z filter.
In order to perform the MQMAS measurement, adjust each power level first.
■ Adjustment of the high power output
The high power output used in the MQMAS measurement is the maximum power that the
probe can endure. Usually, the obs_amp_pulse is set to 100% with the attenuator value
written in the probe file. Also, the 90° pulse width for the sample is measured for that
power.
1.
Set the sample.
2.
Perform spinning.
3.
Load the pulse sequence single_pulse_solid.jxp to the Experiment Tool.
4.
Set obs_angle_prep to 90 deg.
The 90° pulse width is not equal to 1/4 of the 360 ° pulse width because of the in-
fluence quadrupolar interaction of the nucleus having the half-integer spin. There-
fore, use the value of the strongest signal intensity as the 90 ° pulse width.
5.
Set obs_amp_pulse to 100%.
6.
Set up an array measurement for obs_width_90.
7.
Click the Submit button.
The pulses occur, and the measurement begins.
When measurement ends, the nD Processor window opens automatically.
8.
Perform data processing.
After data processing, the result is displayed by Linearize.
9.
Seek the obs_width_90 having the strongest signal intensity in the spectrum
after carrying out Linearize processing.
This value is the 90 ° pulse width of the sample.
NMECAXS_V50-SLD-2
Refer to the user's manual "Data processing" for the procedure for processing
the data obtained by the array measurement.
7 MQMAS METHOD
7-5
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