Re: Carbon-13 decoupler calibration
Rainer Kerssebaum (rke@bruker.de)
Fri, 21 Nov 1997 13:56:42 +0000
Dear Keith,
> I'm trying to puzzle out the workings of the decp90 and decp90lo pulse
> programs for the purpose of calibrating the carbon-13 high and low power
> decoupler pulses. I'm using an AMX-300 on which paropt gives a carbon-13
> transmitter 90 degree pulse width of 7.5 usec. I expect that the C-13
> high power decoupler 90 degree pulse width shouldn't be far off that
> value.
>
> Given this information, my question is why does decp90 give me a value
> of 18 usec. for the high power C-13 decoupler pulse width (using C-13
> enriched sodium acetate). Also, when trying to do the low power decoupler
> 90 degree pulse width calibration using decp90lo I cannot seem to get the
> program to work properly. Using a value of dlo of 18 db the antiphase
> doublet decreases in intensity to a minimum and then increases *without*
> changing phase. Any other values of dlo produce even poorer results and in
> no case can I completely null the doublet and reverse its phase.
>
> Is there a parameter which controls the power output of the BSV-10 in
> high power mode such that it can be varied in, say, 1 db increments? If
> so, this might explain my problems with decp90. As for decp90lo I am
> mystified.
There is a parameter XL which controls a fixed 3 dB (or 5 dB depending
on frequency) attenuator in the output of the BSV-10. Is it possible
the settings in the 2 datasets are different ? XL=0 means attenuator
is off, any other setting means on.
The decp90lo problem sounds like you are not on-resonance for 13C.
Yours
Rainer
--
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... ... Dr. Rainer Kerssebaum
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