>
> I have the feeling that I am not the only person with probes that
> experience this. Interestingly enough, if you happen to have the Bruker NMR
> Training Course Manual called "A Practical Guide to Setup and Operation of
> the AMX/ARX Spectrometers - CPU/4 Version" (mine is dated Feb. 25, 1994},
> look on page 4 of Chap. 3. The plot looks as though the proton 90 deg pulse
> is ~9 usec and the 180 deg pulse is about 22.5 usec. Also on page 9 of the
> same chapter, the C-13 90 deg pulse is about 10 or 11 usec and the 180 deg
> pulse is about 26 usec. I've always been curious as to whether other Bruker
> users have observed this sort of thing.
>
>
Dear Jane,
An effect similar to the one you describe can result from T1,
particularly if you are using de-gassed "test" samples and a routine like
PAROPT. How serious the effect is will depend on the T1 of the
particular sample and the recycle time you use in your calibration, and
can therefore appear to change from probe to probe and nucleus to
nucleus. This may not be your problem, but you should check and
eliminate it first. To avoid this problem I prefer to calibrate on a 360
degree pulse, which does not suffer from T1 effects to anything like the
same extent.
Alan.
Alan M Kenwright Phone: +44-191-374-2595
IRC in Polymer Science and Technology FAX: +44-191-374-4651
University of Durham
South Road
Durham DH1 3LE
UK