4.3 Multipulse Experiments and User Library
01-999162-00 C0402
VNMR 6.1C User Guide: Solid-State NMR
60
4.3 Multipulse Experiments and User Library
The macros for some of the multipulse NMR sequences are located in
maclib
. The
macros for other multipulse NMR sequences are located in the user library
userlib
.
4.4 Multipulse Tune-Up Procedure (FLIPFLOP)
The pulse sequence
flipflop.c
is used to perform both the XX (FLIPFLIP) or X-X
(FLIPFLOP) tune-up experiments.
To tune up for CRAMPS or other multiple-pulse sequences accurate measurement the
proton 90
o
pulse and minimization of the effects of RF inhomogeneity is required. The
procedure that follows uses a narrow-line liquids sample with repeating X pulses and
interleaved acquisition.
Prepare the Sample
1.
Fill a small glass bulb with a single-line protonated solvent such as benzene, dioxane
or water.
An organic solvent is recommended since its affect on probe tuning is similar to that
of an organic solid. Add a bit of the relaxation agent CrAcAc (not provided) to the
organic solvent to shorten T
1
.
2.
Center the bulb in the coil.
Alternatively, a small solids sample of RTV (silicon rubber caulk from the hardware
store) will provide a
1
H linewidth sufficient for tuning. Spin the RTV at about 2 kHz
during these measurements.
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