4) Measuring 90 and 180-degree tip angles (in VnmrJ). Be sure to tune the probe!
Any modern NMR experiment other than routine 1H will require calibrated 90 and 180 degree pulses. On these instruments, probe calibrations are measured for standard samples and saved in the probe file. Assuming you prepare your sampler properly, and assuming the probe is tuned and matched, 90% of the time these saved values will work well for your samples. But in some cases, for example slaty or acidic samples, the calibrated values may not be correct for your particular sample. If so, you may need to calibrate the pulse lengts yourself so that any future experiment (COSY, HSQC, Solvent suppression, Wet1D, 1D NOE, etc) will be collected properly. In addition to addressing the concepts of 90 and 180 degree pulses, this video shows how to manually measure the 90 and 180 degree pulse lengths. Tip… Be sure the probe is tuned!!
