Bruker BioSpin Solid State NMR, User Manual

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108 (327) BRUKER BIOSPIN User Manual Version 002
Basic CP-MAS Experiments
Figure 7.3. Comparison of a CPTOSS and CPMAS Experiment
Figure 7.3.
compares a CPTOSS experiment (lower spectrum) to a CPMAS ex-
periment (upper spectrum) on tyrosine HCl at 6 kHz sample rotation using a 4 mm
CPMAS double resonance probe at 500 MHz with 16 accumulated transients.
The sequence is not perfectly compensated for experimental artifacts and if per-
fect suppression of SSB is required, one can use a 5 pulse sequence with a long
phase cycle, requiring a minimum of 243 transients for complete artifact suppres-
sion using the pulse program
cptoss243
, where the extension .av is added in
case of the AV2 console.
Figure 7.4.
shows the advantage of the well compensat-
ed TOSS sequence with its 243 phase cycle steps over the above 4 pulse se-
quence. Besides the better compensation, the
cptoss243 pulse sequence is also
shorter and uses only 1 instead of 2 rotor cycles. This pulse program can be used
with fairly high spinning speeds, up to about 12.5 kHz sample rotation, depending,
of course, on the width of the employed
π
– pulses.
Figure 7.5.
shows for a com-
parison the results obtained with the 4 pulse sequence with 256 scans.