Bruker BioSpin Solid State NMR - 4.4 Calibrating 13 C Pulses on Adamantane and Shimming the Probe

Basic Setup Procedures
User Manual Version 002 BRUKER BIOSPIN 73 (327)
Calibrating 13C Pulses on Adamantane and Shimming the Probe 4.4
A high power decoupling experiment on
13
C of adamantane is used to measure
13
C pulse parameters.
NOTE: For experiments where long decoupling pulses on protons are executed,
the proton preamplifier must be bypassed, i.e. the transmitter should be wired to
the probe directly (via the proton bandpass filter) without going through the pre
-
amp if a high power proton preamplifier is not available. For HP-HPPR modules
1
H/
19
F this is not absolutely necessary, but recommended. For HPLNA
1
H mod-
ules it is not required to bypass. Note that when bypassing the preamp which at-
tenuates by about 1 dB, the proton power levels should be corrected by adding 1
dB to the pl-values.
Type edasp in the command line. You should get a display like in Figure 4.11..
Click on SwitchF1/F2 to set for
13
C observation with proton decoupling. Load the
pulse program hpdec. Set cpdprg2=cw. Set pl12 to the power level that yields a
4.5 µsec proton pulse. Set pl1 such that in ased the power displayed is 200W for
13
C (7mm probe), 150W (4mm probe) or 80W (2.5 mm probe). If the green dot is
not visible in edasp for the
13
C channel, set pl1 to 12 dB (1 kW transmitter), 9 dB
(500W transmitter) or 7 dB (300W transmitter) for any probe. Make sure the pro
-
ton channel is tuned (wobb high) and the carbon channel is also tuned (wobb).
With d1 = 4s, rg = 256 swh = 100000, td = 4k, o2 set to be on resonance on the
adamantane protons as found above, accumulate 4 scans. Set the carrier fre
-
quency between both adamantane
13
C peaks. Reduce the spectral width swh to
50 kHz, set aq =50 msec.
Acquire 2-4 scans and define the plot limits (as shown in Figure 4.14.) for the
larger of the two peaks. Define the plot limits and determine the 90 degree carbon
pulse p1, using popt. Recalculate pl1 for a 4.5 µsec carbon pulse using calcpow
-
lev.
Pulse continuously using gs and shim the z gradient for highest FID integral.
The gradient settings can be conveniently changed in the setsh display. Figure
4.18. and Figure 4.19. show the adamantane
13
C FID without shims, with z-shim
adjusted and the corresponding setsh displays.