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7 MQMAS METHOD
Fig. 7.4 The pulse sequence of the 3QMAS with the Z filter, and magnetization
In the 3QMAS with the Z filter, the spin system is excited to 3 quantum by the first pulse
in the same way as with the usual 3QMAS, and evolved during time t1 by using phase
cycling in which only 3-quantum coherence remains. Then, 3-quantum coherence is
converted to zero quantum coherence, and signals other than the Z-axis are eliminated af-
ter the second pulse. Finally, the signal of the Z-axis is excited to single-quantum coher-
ence by the last pulse in order to detect it.
In the 3QMAS with the Z filter, since the coherence transfer pathways are 0 → 3 → 0 →
– 1 and 0 → – 3 → 0 → – 1, it has an advantage of making it hard for artifacts to appear.
Moreover, since the selective excitation pulse is used for the last single pulse, the side
band signal does not appear on the direct-observation axis.
7-4
RF Pulse
PW1
t1
Coherence Order
5
4
3
2
1
0
-1
-2
-3
-4
-5
transfer pathway
PW2
ZF
NMECAXS_V50-SLD-2
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