UW CHEMISTRY NMR

Dear Users

You might have noticed that Topshim is taking an abnormally long time to converge.  This has nothing to do with the Topshim program, but it is caused by the  magnet’s cryogenic shims still drifting towards their ultimate equilibrium.   Newly charged superconducting magnets will take a while to reach a rock steady state, and it can take up to a month for the whole system to reach its ultimate stable state.

Notwithstanding this, the instrument is very much usable, if you follow these helpful steps :

• Spin the sample before you run topshim.   The isolated command ‘topshim’ will perform optimization only for the Z-axis field variation.  The spinning sample will provide the field averaging for the XY plane.
• You can record your spectrum while the sample is spinning.
• Always turn ON the Autoshim,  if it is not ON already. (If you need help in figuring this out, please contact one of us)

NMR Facility

4.29.25