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5.4
METHOD OF MEASURING NUCLEUS OF SPIN 1
For a nucleus whose nuclear spin is 1 and asymmetry parameter η is nearly equal to zero,
a high-resolution spectrum is obtained by MAS. The asymmetry parameter is the pa-
rameter showing the asymmetry of the electric field gradient around the nucleus. For
deuterium substituted for
over,
6
Li is also measured with high resolution by MAS.
Usually, a sample of a rare spin system is measured by using a single pulse.
Mainly used sequence
• single_pulse_solid.jxp
5.5
METHOD OF MEASURING NUCLEUS OF
HALF-INTEGER SPIN
For the nuclei that have half-integer spin other than 1/2 spin, such as such as 3/2 and 5/2,
the peak due to central transition can be narrowed by MAS, because the central transition
is not affected by the first-order quadrupolar interaction. Moreover, since the residual
second-order quadrupolar interaction is inversely proportional to the magnetic field
strength, broadening of the line is suppressed by the high magnetic field, and the
separation capability of the peaks increases. By using the NMR instrument with a
high-magnetic field, even for a nucleus like
a certain extent. Although available spin systems are limited, the analysis for the some
material can be carried out.
However, the broadening of the line by residual second-order nuclear quadrupolar inter-
action has prevented separation of the peaks for many samples. Some techniques that re-
move this residual interaction in a nucleus of a half-integer spin and acquire a high-reso-
lution spectrum have been proposed.
Three typical techniques for obtaining a high-resolution spectrum are the DOR (Double
Rotation) method, the DAS (Dynamic Angle Spinning) method, and the MQ (Multiple
Quantum)-MAS method. Because the DOR method and the DAS method need a special
probe for these techniques, they are not generally used. Since the MQ-MAS method can
be performed using a MAS probe that is widely available, this technique is easy to use.
Usually, a sample of a half-integer spin system can be measured using a single pulse un-
der high-speed spinning or the MQMAS method.
Mainly used sequences for measurement
• single_pulse._solid.jxp
• mqmas_3Q_z.jxp
• mqmas_5Q_z.jxp
Mainly used sequences for adjustment
• mqmas_3Q_z_setup. jxp
• mqmas_5Q_z_setup. jxp
NMECAXS_V50-SLD-2
H in an organic compound, η can be considered as 0. More-
1
27
Al, the peak separation becomes possible to
5 MULTINUCLEAR MEASUREMENT
5-3
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