Bruker BioSpin Solid State NMR - Table 5.1. Acquisition Parameters

Decoupling Techniques
User Manual Version 002 BRUKER BIOSPIN 95 (327)
The figure above shows homonuclear proton decoupling on center packed ada-
mantane sample rotating at 7 kHz, 100 kHz
1
H decoupling field. Note that good
B
1
-homogeneity is required. Use a CRAMPS spinner (12 μl sample volume in a
4mm spinner).
Setting up the experiment:
1. Use center packed adamantane in a CRAMPS rotor, unlabeled and a spinning
rate of 10 kHz for adamantane.
2. Start from a data set with well adjusted HH condition on adamantane.
3. Generate a new data set with edc.
4. Readjust decoupling power pl12 and p3, pcpd2 for 70-100 kHz RF field, de-
termine the precise RF field (preferably via a 360° proton pulse p3).
5. Load the pulse program fqlg. This uses frequency shifts with simultaneous
phase shifts for FSLG-decoupling at pl13.
6. Set pl13 to achieve the same RF-field as measured in step 4, set cnst20 to
the value of RF field in Hz. The pulse program contains the include file <lg
-
calc.incl> which calculates the required frequency shifts to either side (shown
in ased as cnst22 and cnst23). Cnst24 provides an additional overall offset to
compensate for phase glitch. With proper probe tuning and 50
match,
cnst24 should be close to zero.
7. Set acquisition and processing parameters according to Table 5.1. and Table
5.2..
A spectrum like in fig. 4 should be obtained. If the splitting is worse, optimize with
pl13 and cnst24. Usually, somewhat less power than calculated is required.
The FSLG decoupling scheme is also implemented as cpd-program cwlgs. The
include file lgcalc.incl is also required. With cpdprg2 = cwlgs, the standard cp
pulse program can be used. The ZGOPTN –Dlacq (ased) should be set in order
to allow decoupling times >50 ms.
Table 5.1. Acquisition Parameters
Parameter Value Comments
pulprog fqlg AV3, use fqlg.av for AV1+2.
d1 4 s Recycle delay.
ns 4-16 Number of scans.
aq 80 ms Acquisition time.
spnam0 ramp.100 or, ramp70100.100 For ramped CP.
pl12, p3 set for p3=90°
sp0, pl1 set for cp
p15 5-10m
pl13 set for 70-100 kHz Optimize for best resolution.
cnst20 70000-100000 Equals the applied RF-field.
Ω