Chapter 6. Solid-State NMR Experiments
83
VNMR 6.1C User Guide: Solid-State NMR
01-999162-00 C0402
Measurement of
13
C
T
1
ρ
Measurements of the spin-lattice relaxation time in the rotating frame (T
1
ρ
) are possible
using the standard XPOLAR pulse sequence. The parameter
p3
is the spinlock time after
cross-polarization. Typical values for
p3
range from 50 to 5000 microseconds.
is a diagram of the sequence.
To analyze a T
1
ρ
experiment of the decay time constant, enter:
analyze('expfit','p3','t2','list').
The
analyze
command has four arguments. The first argument is
expfit
. The
analyze
program provides an interface to the curve fitting program
expfit
, supplying
it with the input data in the form of a text file
analyze.inp
in the current experiment.
analyze.inp
is generated by a line listing of the peaks of interest in a spectrum and by
the
fp
command, which measures the peak height of each peak in an array of spectra. The
second argument of
analyze
is the name of the arrayed parameter, which in the case of
13
C T
1
ρ
experiments using the
xpolar
sequence is the parameter
p3
(for
xpolar1
, use
pchro
). The third argument is the type of analysis to be performed, for example use
t2
for the exponentially decreasing data points of a T
1
ρ
experiment. The fourth argument,
list
, results in the construction of the file
analyze.list
, where the summary of the
data analysis and calculations are stored in the current experiment. A hard copy can be
Figure 31. Protonated Carbon Suppression Sequence
13
C
1
H
level2
xpol='y' pdp='y'
d1
pw
level1
p2
d2
1/srate
2*pw
1/srate
Figure 32. Rotating-Frame Spin-Lattice Relaxation Measurements Sequence
13
C
1
H
d1
pw
level1
p2
level2
xpol='y'
p3