decrementing delays

Jose Martins (jose@HNMR.vub.ac.be)
Thu, 3 Oct 1996 10:30:31 +0100

Hi there,
In a constant time application , one can either increment or decrement the
associated delay, to create evolution of chemical shift or couplings (Depending
on the situation) duing a fixed time period. This works nicely, but for my
application, tis means I have to start with the 180 in the middle of the
period, yielding 0s evolution time and essentailly no signal. Since I am
worlking at natural abundance, this means throwing away half a day of
instrument time.
So the next time I did the experiment, I thought of starting with the 180 pulse
at the end of the fixed period, and decrementing my delay (d10, determing the
third dimension). In this way, I start with maximum signal and end with a small
delay, not necessarily zero.
I of course made sure to put a dd10 (decrement delay10) line at the good
position int he loop. Alas... 3D FT clearly shows only peaks centered aorund
F1=0 in the third dimension.
So has anyone had the same experience with decrementing delays in Bruker pulse
programs? I am using the version of UXNMR of october 1994 on an AMX500.
In retrospect, I could have placed my 180 degree 13C pulse at the beginning of
the fixed delay, allowing to incerment the delay. Unfortunaltey, I only thought
of that, after 4 days of acquisition...
Nevertheless, the dd command should work.

Thanks for listening (or should I say reading)

jose

-- 
Jose Martins Ph.D
High Resolution NMR Centre
HNMR (ORGC)
Vrije Universiteit Brussel
Pleinlaan 2, B-1050 Brussel
phone: 32-2-629-33-05
fax  : 32-2-629-32-81
e-mail jose@hnmr.vub.ac.be