On Wednesday 07 October 2009 05:14:44 pm Bruce Ravel wrote:

I have run 14 samples (each 4 times) on the beamline, and I'm looking for a shift in the oxidation state of Uranium (4+ to 6+).  I'm not sure and can't seem to find any literature on how significant the shift must be to prove anything.

That surprises me. The literature on XAFS studies of uranium valence is enormous, much of it written by people who read this mailing list. Hopefully one of those fine people will offer up a wealth of suggestions for places to look.

Of the 14  samples the uranium peaks for almost all are the samples are at 17160 eV, however a couple samples are at 17158 and another at 17159 eV.  The beamline was filtered for both Thorium and Strontium and a zirconium foil standard was implemented.  I have aligned all of the zirconium standards peaks, and still have this slight shift in the energy of uranium. Do you have any insight?

See my comment below on the value of attaching a small project file which demonstrates the problem.

Also, this is more of a software question.  I'm not sure why, but about half of the samples flip their orientation 180 degrees (from positive y to negative y) when "normalizing" them.  But when I'm trying to display several samples at once about half are showing positive peaks and half are negative peaks.  For instance, samples 10, 3 and 1 don't flip when normalized, however all of the other samples do.

I don't really know what you are talking about, but I suspect that you have poorly chosen values for the pre-edge or nromalization parameters: http://cars9.uchicago.edu/~ravel/software/doc/Athena/html/bkg/norm.html This is a situation where preparing a small project file which deomnstrates the problem and posting it along with your question to the mailing list is the most productive course of action. With a project file, one of us has a chance to replicate your problem on our own computer. It is really important to remember that if the person of whom you are asking your question cannot replicate the problem, it is highly unlikely that person can actually answer your question. One of the points of the Athena project file is to allow exactly this sort of communication.

If this isn't a good enough explanation I could send files or we could trouble shoot over the phone.

I don't do telephone support for the software. There are far too many users for that sort of thing. Don't call. Use this mailing list. B -- Bruce Ravel ------------------------------------ bravel@bnl.gov National Institute of Standards and Technology Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2 Building 535A Upton NY, 11973 My homepage: http://xafs.org/BruceRavel EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/