Hi Tony, The approach that I like to take, is to vary the choice of E0 in the background subtraction step so that the chi(k) spectra are well aligned with each other and the theory. Then only one Ezero parameter is needed. Cheers, Shelly

-----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit- bounces@millenia.cars.aps.anl.gov] On Behalf Of Scott Calvin Sent: Wednesday, February 14, 2007 7:52 AM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] question about Eo and simultaneous fitting

Hi Tony,

A quick answer before I try to fight my way through an ice storm to get to work. :)

Fitting the three spectra simultaneously makes sense, but if oxidation state is expected to be different, then you really need different E0's.

As far as doping, it depends on the details. In some cases, it may require a different E0's, in others, not. Of course, you can try it both ways, and see what the fits think.

--Scott Calvin Sarah Lawrence College

At 05:04 AM 2/14/2007, you wrote:

...

Hi,

first I would like to thank all experienced people answering in this forum!! I have learned really a lot from you.

And now my question: Should I fit EXAFS spectra of a doped material and the same material, but oxidized and reduced (three spectra) simultaneously? In my opinion: yes, as I am looking for small differences. Is varying one Eo for the three samples the right approach? I am also wondering, should I vary one Eo for samples with different doping concentrations?

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