Hi Silvio, There are a number of ways to reduced the big spike at low k. Sometimes just tweaking E0, kmin, kmax, and k-weight are enough. My favorite approach is to use the model as a theory in the background subtraction procedure. I talk about how to do that in this presentation file that I posted on the XAFS.org page: http://www.xafs.org/Tutorials. The pdf file is called: Basics_of_XAFS_analysis.pdf. You will want to follow Example #1 Aligning data and theory. The screen shots are a bit outdated. Some of the parameters in Athena are now hidden under the "Show additional parameters" button. Good luck, Shelly --------------------------- Shelly Kelly Argonne National Laboratory Bldg 203, RM E113 9700 S. Cass Ave Argonne, IL 60439 Molecular Environmental Science Group www.mesg.anl.gov skelly@anl.gov phone: 630-252-7376

-----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit- bounces@millenia.cars.aps.anl.gov] On Behalf Of Silvio Levy Sent: Wednesday, October 18, 2006 12:01 PM To: Ravel, Bruce D. Cc: XAFS Analysis using Ifeffit Subject: [Ifeffit] Athena bug and a question

Bruce - thanks a lot for your post. I've encountered this bug a few times, but I thought it might be a problem with my machine; in any case I could never replicate the problem and file a bug report.

I have another question to the list - how do I get rid of a spike at low k? See for instance http://www.msri.org/~levy/files/Cinnabar/cinnabar.prj

If you open this file with Athena and plot in k-space, there is a big spike at low k; I haven't worried about this too much, but now that I'm starting to show other people my work, I'd like to get rid of it. Presumably my background subtraction is at fault, but how to fix it? The spike also messes the normalization.

Thanks,

Silvio

_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit