On Thursday 17 June 2004 03:17 pm, Ahmed M Shahin wrote: AM> Hello, I would like to ask a very quick question and I would AM> appreciate if someone can help me. While running XANES fitting AM> for mixed valence state metals such as cerium (3/4), should I use AM> two arctangent functions with selected group of Lorentzian AM> functions or I have to use only one arctangent function with a AM> group of Gaussian functions? I would appreciate if someone give AM> some advice. Yours, Ahmed The most recent version of Athena allows you to use most any combination of arctangents and peak functions. There are those that say using two arctangents is a good idea for a sample such as yours. I would recommend trying various different ways of simulating/fitting the data with lineshapes and find the combination that best describes all your data. Since these lineshape fits are, at best, somewhat heuristic, I think the most important thing is that you treat all of your data in a *consistent* manner so that the trends in the data are consistent and intepretable in a consistent manner. A caveat -- I have not tested the peak fitting routine in Athena extensively in any case and certainly not in fits involving two arctangent functions. I put in the ability to do two or more arctangents at Dave Barton's request. I was kind of hoping that he would try it out and, as he has so often in the past, let me know if anything is wrong. Perhaps Dave has a comment? ;-) B -- Bruce Ravel ----------------------------------- ravel@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/