7 MQMAS METHOD
■
Adjustment of the selective excitation pulse
The pulse for the Z filter uses the power of selective excitation. Select the RF intensity so
that the 90
°
pulse of the target sample may be 12 to 15
μ
s. Adjustment of the pulse width
is performed for the highest signal intensity in the same way as the adjustment of the
high-power output pulse.
1.
Set the sample.
2.
Perform spinning.
3.
Load the pulse sequence
single_pulse_solid.jxp
to
Experiment Tool
.
4.
Set
obs_angle_prep
to 90
deg
.
5.
Set
obs_width_90
from 12 to 15
μ
s.
6.
Set up an array measurement for
obs_amp_pulse.
7.
Click the
Submit
button.
The pulses occur, and the measurement starts.
If the measurement ends, the
nD Processor
window opens automatically.
8.
Perform the data processing.
Refer to the user’s manual “Data processing” for the procedure for processing
the data obtained by the array measurement.
After data processing, the result is displayed by
Linearize
.
9.
Seek the
obs_amp_pulse
having the strongest signal intensity in the spec-
trum after carrying out
Linearize
processing.
This value is the power of the Z filter.
If initially you set
obs_amp_pulse
to a higher value, and perform the array
measurement, you might take a 270
°
pulse or 450
°
pulse incorrectly. To pre-
vent this, set the initial value for the array measurement at a smaller value.
7.3.2 Adjustment of Parameters
To adjust the MQMAS measurement, search for the conditions that give the strongest
signal intensity by using the sequence for adjustment. For the 3QMAS with the Z filter
measurement, the following adjustment sequence is used.
Mqmas_3Q_z_setup.jxp
1.
Set the sample.
2.
Perform spinning.
3.
Load the pulse sequence
mqmas_3Q_z _setup.jxp
to the
Experiment Tool
.
Fig. 7.5 Pulse section of the Experiment Tool
7-6
NMECAXS_V50-SLD-2
