Hi again to everybody, Thank you for the answers. They are all helpful. Just to specify a little more: all samples are measured at the K edge of the doped metal oxide. I expect relation between the coordination environments of the different samples as the reduced and oxidized samples are mixture of two formal oxidation states. I will try with different Eo and the Shelly's aligning-suggestion. Tony ----- Original Message ---- From: Matt Newville To: XAFS Analysis using Ifeffit Sent: Wednesday, February 14, 2007 9:01:29 PM Subject: Re: [Ifeffit] question about Eo and simultaneous fitting Tony --

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?

I think you need to be more specific about what your samples are and what you're trying to learn from them. For example, I could read your question as meaning you have samples of Mn K edge for Mn doped into silicon ("a doped material") Si K edge of pure silicon ("same material, reduced") Si K edge of quartz ("same material, oxidized") In which case, I don't see that see much to be gained by fitting the spectra together. In general, one fits multiple spectra together when it is expected that there is a relationship between the different coordination environments, most usually a simple relationship between the g(R)'s for the different samples. E0 is typically different for each sample. There are situations where they can be constrained to be the same, such as spectra are all on the same sample at different temperatures. For more specific answers, please ask more specific questions. --Matt _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit ____________________________________________________________________________________ Looking for earth-friendly autos? Browse Top Cars by "Green Rating" at Yahoo! Autos' Green Center. http://autos.yahoo.com/green_center/