2 FUNDAMENTALS OF SOLID-STATE NMR MEASUREMENT
2.5.2 Notes of Cross Polarization
Since signal intensity depends on the contact time in the CPMAS method, it is necessary
to search for the optimum conditions (
)
Sect. 4.3).
Moreover, the cross-polarization condition under high-speed MAS depends on the spin-
ning speed. The Hartmann-Hahn condition, taking into account the spinning speed
ω
un-
der high- speed MAS, is as follows.
|
γ
I
B
1
I
| = |
γ
S
B
1
S
| + n
・
ω
r
（
n =
±
1,
±
2
）
Thus, since the cross-polarization condition under high-speed spinning differs from the
cross-polarization condition under low-speed spinning, it is necessary to take care during
CPMAS measurement under high-speed spinning.
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