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4 ADJUSTMENT OF MEASUREMENT CONDITIONS AND PROCESSING CONDITIONS
4.5
SETTING SAMPLING POINT (X_POINTS)
The parameter x_points specifies the number of sampling points to acquire FID data.
For a solid-state NMR measurement, this parameter is used to adjust the decoupling time.
Since decoupling time is the same as acquisition time, it is expressed as x_acq_time.
High-power RF will be input to the probe during x_acq_time.
In order to reduce the load of the probe, it is necessary to shorten x_acq_time. However,
if x_acq_time is too short, the FID signal will not be acquired. Ideally it is best that
x_acq_time is as short as possible while still acquiring the entire FID signal. A good
example and a bad example are shown in the following figure. As estimates, x_acq_time
is about 20 ms in polymers and about 40 to 100 ms in crystals.
NMECAXS_V50-SLD-2
Good example
Undesirable example: x_acq_time is too long.
Fig. 4.4 Good and bad examples of acquisition time
Bad example: x_acq_time is too short
4-5
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