Iztok, This is good stuff. Mulitelectron features definitely throw at least a small wrench in a typical background substraction routines that only substract smooth, broad features using splines. My naïve questions are: 1) What chemical elements show a sizable contribution from a multielectron feature that could skew spline based EXAFS data analysis routines? 2) Are there any examples in the literature where a spline-based EXAFS analysis (i.e. bond lengths, coordination numbers with statistics) is performed on a more complex system than with and without the removal of these multielectron features as a comparison. Dave

-----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Iztok.Arcon@p-ng.si Sent: Wednesday, July 13, 2005 10:21 AM To: bravel@anl.gov; XAFS Analysis? using Ifeffit? Cc: QY ZML; XAFSA Analysis usingI Ifeffit Subject: Re: [Ifeffit] multielectron transition Importance: Low

Dear Bruce

An example of treating atomic absorption background including large multielectron features in L edge spectra of Ce is given in the attached paper. Full atomic absorption background for nearby elements Cs and Xe can be seen in the second attached paper. Some other useful references on this topic are given below:

J. A. Solera, J. Garcia, M. G. Proietti, Phys. Rev. B 1995, 51, 2678–2686.

A. Kodre, I. Arčon, M. Hribar, M. Štuhec, F. Villain, W. Drube, L. Troeger, Physica B 1995,208&209, 379–380.

J. Padežnik Gomilšek, I. Kozjek Škofic, N. Bukovec, A. Kodre, Thin Solid Films 2004, 446, 117–123.

E. Fonda, D. Andreatta, P. E. Colavita, G. Vlaic, J. Synchrotron Rad. 1999, 6, 34–42.

also some our references for atomic absorption spectra of K edge exafs:

A. Kodre, I. Arčon, J. Padežnik Gomilšek, R. Frahm Multielectron excitations in x-ray absorption spectra of Rb and Kr J. Phys. B: At. Mol. Opt. Phys. 35 (2002) 3497-3513

A. Kodre, I. Arčon, J. Padežnik Gomilšek, A. Mihelič Atomic absorption background in EXAFS spectra of Rb in inter-alkaline alloys Physica Scripta. Vol, T115, (2005) 218-220

A. Kodre, R. Prešeren, I. Arčon, J. Padeznik Gomilšek, M. Borowski, A study of transferability of atomic background on EXAFS spectra of simple gaseous compounds of As, J. Synch. Radiation 8 (2001) 282-284

R. Prešeren, A. Kodre, I. Arčon, M. Borowski, Atomic background and EXAFS of gaseous hydrides of Ge, As, Se, and Br, J. Synch. Radiation 8 (2001) 279-281

There are many other papers of different authors on the multielectron photoexcitations (see references in above papers). Additional information on multielectron photoexcitations in exafs spectra of L and K edges of different elements and some subtraction procedures can be found also on the dedicated web site of our group:

http://www.p-ng.si/~arcon/xas/mpe/mpe5.htm best regards and congratulations for well supported program packages for exafs analysis. Iztok Arcon

On Tuesday 12 July 2005 11:18, QY ZML wrote:

...

I am analyzing EXAFS of some rare earth systems. It is known that there are ?multielectron transitions in these systems. So, I want to know how to subtract multielectron process contribution generally and if ATHENA has a feature to do this. ?Thank you very much.

Athena does not currently have a feature for doing this. Drat!

I would be willing to implement something empirical for doing this. I would like to see a discussion here on the mailing list of the merits of different approaches. Since I have never given this very much thought, I am not with any strong opinions for how it should (or should not) be done. But I can certainly consider implementing it.

B

-- Bruce Ravel ----------------------------------- bravel@anl.gov -or-

ravel@phys.washington...edu

*** My cell phone number has changed. Please ask if you need the new number

Environmental Research Division, Building 203, Room E-165 Argonne National Laboratory phone and voice mail: (1) 630 252 5033 Argonne IL 60439, USA fax: (1) 630 252 9793

My homepage: http://feff.phys.washington.edu/~ravel EXAFS software: http://feff.phys.washington.edu/~ravel/software/exafs/

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