Re: [Ifeffit] Linear Combination Fitting using ATHENA

One spectrum was taken in fluorescence mode (maghemite), the other in electron-yield mode. Yes, it's OK to do that on pre-edge subtracted, normalized spectra, which is what I sent. mam ----- Original Message ----- From: Teck Kwang Choo To: XAFS Analysis using Ifeffit Sent: Tuesday, August 13, 2013 5:07 PM Subject: Re: [Ifeffit] Linear Combination Fitting using ATHENA Thanks Matthew for the spectra. Is it correct to use the spectra that was taken in transmission mode (the one you did) to fit those taken in fluorescence mode (my case)? Teck Kwang On 14 August 2013 01:37, Matthew Marcus wrote: Here are reference spectra. The calibration is defined with the Fe metal edge at 7110.75eV. The maghemite spectrum has been corrected for mild overabsorption by reference to magnetite, which is very similar. The magnetite is synthetic Fe3O4 from Aldrich, and done in TEY, so no overabsorption. The maghemite is from oxidation of Fe oxide nanoparticles and has been verified by XRD and comparison with the ETH group's maghemite spectrum. mam On 8/13/2013 1:33 AM, Teck Kwang Choo wrote: Hi all, @Drew Latta: I was wondering why the end members should be magnetite and maghemite. Is it because they are both of inverse-spinel structure, the difference only being that the latter has all Fe completely oxidized into Fe(III)? Would you be able to provide the standard spectra to me if that is the case? Thanks very much! Previously I have only thought of using hematite (alpha-Fe2O3) and FeO as end-members, both representing Fe(III) and Fe(II) respectively without giving much thought to the structure Fe takes. I also had my doubts using magnetite (Fe3O4) as a standard as it is a mixture of both Fe (II) and Fe (III). But thanks to the insights Drew has given, I now think I should take the Fe-coordination environment into account with the use of magnetite and maghemite as standards. @Alexandre and Matthew: I have obtained Mossbauer spectra of some of my samples but like Drew said, it is not straightforward at this point in time. Will see what I can do with the data I have! Thanks for all your responses! It is greatly appreciated! This forum has been more helpful than I thought! Teck Kwang On 13 August 2013 01:34, Matthew Marcus mailto:mamarcus@lbl.gov> wrote: While it's true that Mossbauer is the gold standard for Fe valence determination, access to the technique isn't all that common, and I don't know of any facility that can do it on a micro scale. Is there one? mam On 8/12/2013 7:01 AM, Alexandre dos Santos Anastacio wrote: Hello, maybe that fingerprinting technique would be Mossbauer spectroscopy. The Fe(II)/Fe(III) ratio comes easily and also there are lots of papers about Mg-ferrite, an example: 10.1109/TMAG.2009.2018880 <http://dx.doi.org/10.1109/__TMAG.2009.2018880 http://dx.doi.org/10.1109/TMAG.2009.2018880> Alexandre. _________________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.__gov mailto:Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.__gov/mailman/listinfo/ifeffit http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit _________________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.__gov mailto:Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.__gov/mailman/listinfo/ifeffit http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit -- Teck Kwang Choo PhD Student Department of Chemical Engineering Room 225, Building 36 Monash University Mobile No.: 04-11489904 _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit -- Teck Kwang Choo PhD Student Department of Chemical Engineering Room 225, Building 36 Monash University Mobile No.: 04-11489904 ------------------------------------------------------------------------------ _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit