Chapter 4. CRAMPS/Multipulse Module Operation
69
VNMR 6.1C User Guide: Solid-State NMR 01-999162-00 C0402
4.10 BR24 and CYLBR24 - Multiple Pulse Line Narrowing
(24-pulse cycle)
Br24 (Figure 23) is the usual sequence used for
1
H CRAMPS. CYLBR24 is a modification
that allows quadrature detection with the transmitter in the center of the spectrum. The
sequences are applicable for UNITYplus and
UNITY
INOVA as well as UNITY and VXR-S
with a Sync Module.
Macros
The macro br24 converts a S2PUL or FLIPFLOP data set for BR24. cylbr24 converts
a data set for quadrature BR24. All relevant parameters are preserved if the initial data set
is FLIPFLOP, BR24, CYLBR24, MREV8 or CYLMREV.
Parameters
pw is the 90
o
degree pulse-length, in microseconds.
p1 is the preparation pulse, in microseconds, whose phase is controlled by the parameter
phase1. To minimize the “pedestal” p1 should be set to the 90
o
flip angle and
phase1=135.
tau is the interpulse delay, in microseconds, including pw. The BR24 cycle is 36*tau
long and is repeated np/2 times to build up a FID.
trig='y' for UNITY and VXR-S with a Sync Module. Otherwise trig='n'.
tauc is the cycle time, in microseconds and is the actual dwell time for the FID. tauc is
not changed and is for information only.
mp_at is the sum of all cycles, in microseconds, and is the true acquisition time. mp_at
is not changed and is for information only.
sw=2e6 turns on the fast ADC without analog filters. sw does not determine the dwell time
(see tauc).
scalesw is a scale factor that converts sw=2e6 to the correctly scaled spectral width.
scalesw=(1.0/tauc*sw)*S where S is the multiple-pulse scale factor for Br24
(0.385 for ideal pulses).
rof1 and rof2 (see 4.9 “FLIPFLOP - Pulse Width and Phase Transient Calibration,”
page 68)
prep
d1
'np'/2 times
pw
tau
2*tau
acq
Figure 23. BR24 Pulse Sequence
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