Hello Weixing Zhang,
As regards the -111 Hz, -57 Hz, 57 Hz, and 111 Hz it is possible you are
looking at line-frequency modulation sidebands. They 'should' be at
multiples of 60Hz in the States. In Europe we see them at multiples of 50
Hz. If the problem is great the solution may lie in capacitors in the power
supply but we have had this problem with one of our spectrometers and so far
nothing has helped. P.S. these side-bands will normal have variable phase
and not be in phase with the parent resonance.
As regards the C13 satellites, the reason they are not symmetrical is the
13C versus 12C isotope shift on the the attached proton. Hope this helps
you.
best wishes,
David Grace
Amersham Health, Oslo
-----Original Message-----
> From: Zhang, Weixing [mailto:Weixing.Zhang_at_stjude.org]
> Sent: Wednesday, January 23, 2002 8:11 PM
> To: AMMRL (E-mail)
> Subject: NMR lineshape problem
Hello everybody:
I recently got a nonspin lineshape spectrum with extra peaks.
If I set the main CHCl3 peak at 0 Hz, I saw extra small peaks
at -111 Hz, -57 Hz, 57 Hz, and 111 Hz. Their intensity is about half
of the C13 satellite peaks. What might be the problem?
I closely looked at the normal lineshape spectrum. The two
C13 satellite peaks are located at -109 Hz and 106 Hz.
Does anybody know why they are not symmetrical (-107.5, 107.5 Hz).
Thanks,
Weixing Zhang, Ph.D.
Department of Structural Biology
St. Jude Children's Research Hospital
Voice: (901)495-3169
FAX: (901)495-3032
Received on Thu Jan 24 2002 - 09:18:30 MST