no need to lock and shim if you've done so already on 1H. be sure to check the tuning on BOTH 13C and 1H channels as this can effect spectral quality.
if the 1H tuning is off you'll see splittings where singlets are expected or you might not see any signal at all. if the 13C tuning is off
then the 90 times (excitation) become incorrect and the signal to noise can drop considerably. it is probably a good idea to wobb on 13c
at least once a day to be sure things are ok.
- rpar c13.bbo all - read in the parameter file for the carbon expt set for the .bbo (broad band observe) probe
- ased - use if you'd like to change parameters like the number of scans (ns) etc, else skip
- ns - change the number of scans to 4*n where n=integer. this has to do with the phase cycling in the NMR setup.
- note that the s/n is proportional to the sqrt(number of scans). so if the ns is increased by 4x then the s/n goes up 2x.
- i usually don't run 'RGA' for carbon as this actually leads to worse s/n with this automation. it is probably best just to leave the default 'RG' receiver gain value we set.
- expt - show the experimental run time.
- D1 - D1 is the recycle delay time between scans. it is often set to about 2s if you're only interested in carbons bound to protons.
for quats however it is sometimes necessary for D1 to be set to 10-120s. this allows time for magnetization recovery for carbons with
long T1 times (T1's are important)
- as one changes 'D1' and 'NS' the experimental time increases proportionately. again, you can check with expt
- zg - zero memory buffer and go
Data Processing, see Chp 11 of Topspin 1.3 manual (page 143)
- tr - trace command allows to store current FID which can then be processed while the data is still acquiring
- this command becomes important for long 13C runs. if the s/n is ok you can just halt the expt and save time
- efp - exponential line broadening, Fourier transform and phase (with current params in 'edp')
- lb - change the line broadening weight and run efp again if you like
- apk - autophase correct
- i always manually phase on 13c spectra however
- export/screen dump current window. many users seem to like .png format. see page 81 in manual
and be sure to save like filename.png where the .png tag defines for format (.png, .jpg, .wmf and so on)
please note that peak integrations on 13c doesn't work well. this is due to the varying T1 times among carbons and the fact that only
several data points (its digitized) are used to define the shape of each peak usually.