[Ifeffit] A very quick question

[Bruce Ravel]

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 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/