I would be curious to hear what the conventional wisdom is
on the following issue. I just had to shim a new probe from
Varian to the spinning lineshape spec. My final numbers at
600 were around 0.41/2.96/3.72 Hz at 50/0.55/0.11% peak height.
This compares to the spinning linshape from the factory of
0.40/3.91/7.59. The lineshape I obtained has a minor split
at about 40% of the main peak height. The spinning lineshape
Varian obtained has the same asymmetry but any visible peak
splits are submerged in a much broader peak.
Looking through all of our spec sheets from Varian for
our other probes I see the same behavior. The ns lineshape at
at 0.55/0.11 isn't really that much narrower than the
non-spinning lineshape. Also the peaks are almost always
asymmetric but any visible splitting is submerged in the
broader peak. My instinct is that this approach is wrong and
they one would rather have the much narrower lineshape even
if the splits (on asymmetric sections) become visible. I should
note the I don't have any spinning sidebands larger than the
13C satelites.
My question is basically this. Which is the better approach?
To shim the spinning lineshape for a lineshape that is
narrower than the non-spinning lineshape (I get 0.85/5/9) with
some minor spinning sidebands less than the 13C satelites or
to shim the spinning lineshape to eliminate all of the
spinning sidebands even if this results in a significantly
worse lineshape. Thanks in advance for any insights on this.
Jack
------------------------------------------------------------------------------
Jack W. Howarth, Ph.D. 231 Albert Sabin Way
NMR Facility Director Cincinnati, Ohio 45267-0524
Dept. of Molecular Genetics phone: (513) 558-4420
Univ. of Cincinnati College of Medicine fax: (513) 558-8474
Received on Wed Jun 14 2006 - 14:14:54 MST