Carbon-13 decoupler calibration

Keith Brown (brownk@skyway.usask.ca)
Tue, 18 Nov 1997 15:03:21 -0600 (CST)

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.

Keith

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- Dr. K. Brown brownk@chem4823.usask.ca -
- Department of Chemistry brownk@sask.usask.ca -
- University of Saskatchewan http://chem4823.usask.ca/kbrown.html -
- Saskatoon, SK -
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