I have a problem with the scaling of intensities in exported 1R spectra
that I don't seem to be able to fix.
Few weeks ago I recorded a bunch of 1D files (ca 250) to measure diffusion
coefficients in several samples, I used an ARX-400, with XWinnmr 1.2 running
on an Aspect-1.
So far so good, at first glance all the experiments seemed to work ok. Lazy
as I am I did not want to process all spectra one-by-one, so I wrote a Matlab
program that reads the files in, process them and reports some tables and
graphics. Disappointingly, after getting almost all spectra processed (I
discarded processing the ones we had run for testing purposes) the conclusion
was that no-one of the experiments had worked as desired... well it seemed I
was going to have to re-do all exps once more. But before doing so I've
thought it was worth processing the experiments I knew they had worked, and
here is when my problem happens:
1. the intensities reported on-screen by XWinnmr and those I can read
in the '1r' file do not match (the on-screen intensities decay with
increasing values of 'b')
2. I've discarded I'm messing them when reading the file because they are
the same intensities I get when exporting the '1r' file as JCAMP-DX
file
3. funny enough (not really), the ratio between intensities reported on-
screen and those in the '1r' file gives some interesting values
(see the last column)
-----------------------------------------------------------------
maximum intensity
G_eff ---------------------------
<expno> (G/cm) on-screen JCAMP-DX[1] ratio
-----------------------------------------------------------------
21 4.0 3.41743e+07 2.73394e+08 8
22 6.0 2.97554e+07 4.76086e+08 16
23 7.5 2.52609e+07 4.04175e+08 16
24 9.0 1.85172e+07 5.92549e+08 32
25 10.0 1.47869e+07 4.73181e+08 32
26 2.5 3.53060e+07 2.82448e+08 8
-----------------------------------------------------------------
[1] match the values in the '1r' files as read with Matlab
I'm totally clueless. I'm using the same acquisition parameters throughout
all experiments, so there is nothing that could be explained by a change
in RG, NS, etc. ,
-why this scaling factor?
-where do I find the scaling factor I must apply to retrieve the
correct(?) intensities?
If anyone out there knows the answer I'll be glad to know.
Thanks in advance,
Miquel
Miquel E Cabanas ---------------------------------------------------
SeRMN & BBM - Universitat Autonoma de Barcelona, Catalunya - Spain
MRUI url ------- http://www.mrui.uab.es/mrui
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