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7.2
PRINCIPLE
The MQMAS method is the technique for controlling magnetization transfer by the pulse
sequence and the phase cycling. Here, the two typical MQMAS methods are explained.
■ 3QMAS method
The most fundamental pulse sequence in the current MQMAS method and the pathway of
magnetization transfer are shown below.
Fig. 7.3 Pulse sequence of 3QMAS method, and magnetization transfer
Since this sequence uses 3-quantum coherence, it is called the 3Q (Triple Quantum) MAS
method. The pulse sequence of the 3QMAS method consists of two simple pulses. The
spin system is excited to 3 quantum by the first pulse, and evolved during time t1 by us-
ing phase cycling in which only 3-quantum coherence remains. Finally, its coherence is
converted to single-quantum coherence by a second pulse in order to detect the coherence.
Using such a pulse sequence separates the interaction of anisotropic and isotropic terms.
■ 3QMAS method with Z-filter
The 3QMAS method has taken out two magnetization transfer coherence pathways, 0 →
3 → –1 and 0 → – 3 → –1. However, since these two pathways are asymmetric, the
3QMAS method has a problem in that it easily causes artifacts. In order to solve the prob-
lem, a Z filter is added to the sequence. This is the 3QMAS with the Z filter.
NMECAXS_V50-SLD-2
RF Pulse
PW1
t1
Coherence Order
5
4
3
2
1
0
-1
-2
-3
-4
-5
PW2
t2
7 MQMAS METHOD
7-3
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