Dear AMMRL community,
I am looking for some advice regarding a persistent line shape/shimming problem
on our Varian NMR instrument.
We first noticed that our proton spectra showed unusual broad components/shoulders
underneath otherwise sharp resonances. Initially, I suspected a sample-specific
issue, but the same behaviour is also present with an ethylbenzene in CDCl3 standard.
A few observations:
*
The shoulders/broad components appear on essentially every peak.
*
The main peaks themselves can still look relatively sharp, but there is a broad
underlying component or shoulder.
*
I cleaned the inside bore of the magnet and repeated the experiment, but the problem
remained.
*
I also recorded the ethylbenzene/CDCl3 standard without doing any additional shimming,
and when the spectrum is expanded, the same broadness/shoulder is visible.
*
The spectra shown were acquired with the sample not spinning (0 Hz), so this does not
appear to be caused simply by spinning instability.
*
The instrument locks normally, but the line shape remains poor.
I have attached image showing: ethylbenzene/CDCl3 standard spectrum.
At this point, I am wondering whether this could be related to higher-order
or transverse shims, sample positioning, the probe, or another hardware-related
line shape issue rather than a simple Z1/Z2 adjustment.
Has anyone seen this type of line shape on a Varian system, where every resonance
shows a similar shoulder or broad pedestal? I would appreciate any suggestions
on the best way to diagnose this systematically and which shim terms or hardware
components would be most useful to check first.
Thank you very much for your help.
Best regards,
Venky.
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Received on Fri Aug 14 2026 - 09:14:38 MST