Bruker BioSpin Solid State NMR, User Manual

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248 (327) BRUKER BIOSPIN User Manual Version 002
STMAS
ph1 = 0 2
ph2 = 0 0 2 2
ph3 = 0 0 0 0 1 1 1 1 2 2 2 2 3 3 3 3
ph4 = 0*8 1*8 2*8 3*8 4*8
receiver = 0 2 2 0 2 0 0 2 0 2 2 0 2 0 0 2 1 3 3 1 3 1 1 3 1 3 3 1 3 1 1 3
2 0 0 2 0 2 2 0 2 0 0 2 0 2 2 0 3 1 1 3 1 3 3 1 3 1 1 3 1 3 3 1.
In the stmasdqfz.av pulse sequence this pulse flips the magnetization back along
the z-axis. After a short z-filter delay
D4
a CT selective 90° pulse
P3
creates
transverse magnetization. In the stmasdqfe.av pulse sequence the non-selective
pulse
P2
converts the ST SQ coherence into CT SQ coherence. This is allowed to
evolve for another delay
D6
after which it refocuses into an echo by a CT selective
180° pulse. When either the
D6
before the 180° pulse or
D7
after the 180° pulse is
incremented proportionally to the t
1
period a split-t
1
experiment as described in
chapters 16 and 17 for some MQMAS experiments will be performed.
Figure 19.3. Four pulse sequence and coherence transfer pathway
Four pulse sequence and coherence transfer pathway for the double quantum fil-
tered STMAS experiment with shifted echo acquisition (stmasdqfe.av). Pulses
p1
and
P2
are non-selective pulses. Corresponding power level
PL11
should be set
to achieve around 100 kHz RF field amplitude.
P3
and
P4
are CT selective pulse
90° and 180° pulses of about 20 and 40 µs, respectively, corresponding to an RF
field amplitude of a few kHz. Delay
D0
is the incremented delay for t
1
evolution,
D6
and
D7
can be incremented proportional to
D0
depending on the spin of the
observed nucleus. Phase lists are as follows, incrementation of the phase of the
first pulse is not required because a phase modulated data set is acquired with
FnMODE being QF:
ph1 = 0 180 90 270
ph2 = 0*4 90*4 180*4 270*4
ph3 = 0*16 90*16 180*16 270*16