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7.1
OUTLINE OF MQMAS METHOD
The MQMAS method was proposed by Frydman and Harwood in 1995.
Reference: A.Medek, J.S.Harwood, and L.Frydman. JACS, 117, 12779-12787 (1995).
The MQMAS method has the advantage that it can eliminate quadrupolar interaction
without using a special probe in contrast to the DOR and DAS methods.
Moreover, since it can be adjusted comparatively easily, it can be generally used as the
measuring method.
■ Feature of theMQMAS method
For nuclei having a spin 1/2, information about how many sites exist can only be obtained
by the MAS spectrum. For nuclei having a half-integer spin, the site analysis is difficult
when you only use the MAS spectrum because of the influence of quadrupolar interac-
tions.
As an example, the
Although three different sites exist in rubidium nitrate, such information cannot be ob-
tained from the MAS spectrum. The following figure shows the spectrum measured by
the MQMAS method.
NMECAXS_V50-SLD-2
87
Rb MAS spectrum of rubidium nitrate (RbNO
87
Fig. 7.1
Rb-MAS spectrum (300 MHz)
-10
-20
-30
-40
ppm
87
Fig. 7.2
Rb MQMAS spectrum (300 MHz)
) is shown below.
3
-50
-60
-70
7 MQMAS METHOD
7-1
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