[Ifeffit] Another ATHENA error
ravel at phys.washington.edu
Wed Jan 12 13:19:41 CST 2005
On Wednesday 12 January 2005 09:38 am, Norbert Weiher wrote:
> just to throw another one in :)
The more the merrier!
> ATHENA has the following problem - I make a linear combination fit of two
> spectra and put the result in a group. Then I want to export it using the
> "save groups as..." and.... just get zero's in the file. Using the IFEFFIT
> buffer and saving the corresponding array with the write_data() command
> works fine - maybe there's a renaming bug of the corresponding array?
> Furthermore, the fit looks shifted as soon as written to an array. When I
> fit (the 3rd spectrum in the example with a LC of the first two) everything
> looks nice. The saved LC is, however, shifted compared to the one seen
> during the fit. Furthermore, I cannot change any parameter of this (LC)
You are correct on all counts. The energy shift was due to the fact
that I applied the e0 shift of the unknown data group twice to the LCF
data group. Oops!
I am not completely sure why it was being saved as all zeros, but
fixing other problems also solved that.
You could not change the parameters because, long ago, I had decided
to save the LCF-in-energy data as a detector group. My thought was
that an artificial data group should not be analyzed like real data.
There really isn't a good reason why the LCF-in-energy group should
not be treated that way. For instance, it might be interesting to
remove the background from the LCF-in-energy group to see if its
chi(k) looks like the chi(k) of the unknown data. In any case, I
changed that so now you can treat LCF-in-energy data just like real
All of those fixes will be in the next release.
Bruce Ravel ----------------------------------- ravel at phys.washington.edu
Code 6134, Building 3, Room 405
Naval Research Laboratory phone: (1) 202 767 2268
Washington DC 20375, USA fax: (1) 202 767 4642
NRL Synchrotron Radiation Consortium (NRL-SRC)
Beamlines X11a, X11b, X23b
National Synchrotron Light Source
Brookhaven National Laboratory, Upton, NY 11973
My homepage: http://feff.phys.washington.edu/~ravel
EXAFS software: http://feff.phys.washington.edu/~ravel/software/exafs/
More information about the Ifeffit