2 FUNDAMENTALS OF SOLID-STATE NMR MEASUREMENT
2.2 MAGIC ANGLE SPINNING
Magic Angle Spinning (MAS) is a spinning technique in which the sample rotates on an
axis at 54.74 degree (= arccos
3
/
1
) with respect to the static magnetic field. MAS is the
most fundamental and important technique in the solid-state NMR.
Rotating axis
Sample tube
54.74
°
ν
r
B
0
Fig. 2.1 Magic Angle Sample Spinning
MAS can eliminate all the anisotropic interactions expressed as second-rank tensors (H
D
,
H
CSA
, H
Q
). However, when the MAS frequency is smaller than the interaction, the interac-
tion remains partially or the effect of MAS is not expressed fully. The partially remaining
interaction appears as spinning sidebands or as a broadening of a main peak. Generally,
since the H
D
with
1
H cannot be completely eliminated by only using MAS, high-power
decoupling (
)
Sect. 2.3) is used together with MAS.
2-2
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