Scaling Processing - JEOL JNM-ECA Series User Manual

Thus, you can see that the shift of the sampling starting position of an echo signal causes
the first order phase shift. The shearing process makes this phase shift disappear.
In data processing of MQMAS, after using PN conversion to divide the data into echo
and anti-echo components, the shearing process in the opposite direction is performed on
each component.
7.6.2

Scaling Processing

The second-order quadrupoler coupling shifts the peak position in the MAS spectrum of a
nucleus with half-integer spin. In addition to the shift caused by the second-order quad-
rupoler coupling, the multiple-quantum chemical shielding shifts the peak position in the
isotropic axis of the MQMAS spectrum. Therefore, it is necessary to correct the scaling
of the chemical shift in the MQMAS spectrum.
The scaling coefficient at this time was determined based on the nuclear spin number of
the measurement nucleus (I) and the quantum number of measurement (p).
Scaling factor = | R–p |
R(I、p) = p {36 I (I+1)–17p
In the MQMAS method, because the scaling processing is performed at the end of proc-
essing, y_sweep changes from the value at the measurement. For example, in 5Q-MAS
measurement for spin 5/2-nuclei, since y_sweep becomes 0.14118 times the set value, it
is necessary to set the observation range a little wider when setting it before the meas-
urement.
NMECAXS_V50-SLD-2
2 –10} /{36I(I+1)–27}
7 MQMAS METHOD
7-13