Symmetry Based Recoupling
User Manual Version 002 BRUKER BIOSPIN 183 (327)
8. Maximum magnetic field as proton resonance frequency in MHz. This results
from spin rate requirements for 13C observation (to avoid rotary resonance
conditions) as well as excitation bandwidth considerations.
Spectrometer Setup for 13C 14.2.1
1. Load a CPMAS parameter set for
13
C.
2. Load a uniformly labeled glycine sample and rotate at the desired rotation rate
(see table 1), depending on the recoupling experiment planned and the sample
under investigation. Consider possible rotational resonance conditions in the
sample of interest!
3. Tune and match the probe, optimize the
13
C and
1
H pulse parameters for exci-
tation and decoupling.
4. Use the cp90 pulse program with pl11= pl1 to measure the nutation frequency
for
13
C, in order to calculate the recoupling conditions (see chapter …. Basic
Setup Procedures). Calculate the power levels required by the spin speed (see
table 1) using calcpowlev.
5. Set pl11 back to 120 dB (p1 to zero) and run 1 experiment with 16 (4) scans as
a reference.
Setup for the Recoupling Experiment 14.2.2
1. Create a new experiment and load the appropriate pulse program (spc5cp1d),
use the same routing. Set the appropriate sample rotation rate, as required for
step 14, set cnst31 equal to the rotation rate.
2. Load the power level calculated for the necessary
13
C recoupling B
1
-field into
pl11, set p1 as determined in step 4.
3. Set l0=15 (should be, but need not be, a multiple of 5 for SPC5 or of 7 for PC7,
SC14). This determines the DQ-build-up time (DQ generation). The reconver
-
sion time is usually also controlled by l0, it may however be written such as to
be independently controlled by a different loop counter. For glycine, about
5msec will be the optimum.
4. Set the decoupling program cpdprg1 to cwlg. Set pl13 such as to yield the
desired decoupler RF field during the DQ generation/ reconversion, or set it to
120 if the spin rate suffices to omit decoupling. Set cnst20 = corresponding
decoupling RF field.
5. Optimize pl11 for maximum signal intensity.
6. Optimize l0 for optimum signal intensity. In a multi-site spectrum the optima
may differ for different spin pairs.
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