1H 90 degree pulse width calibration

Due to incomplete relaxation of the spins with a short recycle delay, the signal often does not maximize with a 90 degree flip angle. Additionally, in a sample with a strong solvent signal (such as water), a single 90 degree pulse typically causes the receiver to overflow. It is common to calibrate a 180 or 360 degree pulse and back-calculate the 90 degree pulse width pw (pw=pw180/2 or pw=pw360/4).

1H pulse width is often most sensitive to solvent and temperature while the X-channel nucleus is not as much. Regardless, the 1H channel (or X-channel if used) must be tuned for shortest pulse or for the use of the default setting in a pulse width sensitive experiment.

Detailed 1H pulse width calibration procedure

In the following we assume the power level desired is tpwr=57. Change it accordingly if desired.

Quick Calibration if good estimate is known

Often you could simply array pw around an estimated value with a smaller number of steps and stepsize. Read procedure above for processing, display and calculation.

You can also type: pw=9,35,36,37 to set up a pw array for quick checking of pw360.


Array pw, starting from 2 with 16 steps and a stepsize of 2. Estimated pw360 ~ 32, giving pw ~ 8.


H.Zhou updated Oct 2010