Yes Matthew, I used 7112 eV for my Fe K-edge calibration. I am guessing that is the reason a ~+1 eV shift in your maghemite spectrum is required is required to fit mine. Both pre-edge features match in the sense that they are roughly bound by the same energy values.
On 14 August 2013 17:30, Matthew Marcus <mamar...@lbl.gov> wrote: > ** > That depends on the way you did your calibration. If it really matches, > including the > pre-edge features, with a 1eV shift, then that's what you probably have. > Did you take > into account my calibration, which puts the Fe K-edge at 7110.75eV? Some > people use other > values like 7112eV. > mam > > ----- Original Message ----- > *From:* Teck Kwang Choo <teck.kwang.c...@monash.edu> > *To:* XAFS Analysis using Ifeffit <ifeffit@millenia.cars.aps.anl.gov> > *Sent:* Tuesday, August 13, 2013 9:20 PM > *Subject:* Re: [Ifeffit] Linear Combination Fitting using ATHENA > > Also Matthew, I have found that my sample spectrum is an almost exact > replica of the maghemite spectrum, the only differences being the > absorbance height of the edge-peak (highest peak), which is ok but more > importantly > I have found that there is a +1eV shift of my spectrum relative to the > maghemite one, probably due to slight differences in beamline. Do you think > it is alright to make a +1 eV shift to the maghemite spectrum (or -1eV > shift to my sample spectrum)? > > Thanks. > > Kind regards. > > Teck Kwang > > > On 14 August 2013 10:07, Teck Kwang Choo <teck.kwang.c...@monash.edu>wrote: > >> 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 <mamar...@lbl.gov> 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 <mamar...@lbl.gov <mailto: >>>> mamar...@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> < >>>> http://dx.doi.org/10.1109/**TMAG.2009.2018880<http://dx.doi.org/10.1109/TMAG.2009.2018880> >>>> >> >>>> >>>> Alexandre. >>>> >>>> >>>> >>>> >>>> >>>> ______________________________**___________________ >>>> Ifeffit mailing list >>>> ifef...@millenia.cars.aps.anl.**__gov <mailto: >>>> ifef...@millenia.cars.**aps.anl.gov <Ifeffit@millenia.cars.aps.anl.gov> >>>> > >>>> http://millenia.cars.aps.anl._**_gov/mailman/listinfo/ifeffit < >>>> http://millenia.cars.aps.anl.**gov/mailman/listinfo/ifeffit<http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit> >>>> > >>>> >>>> ______________________________**___________________ >>>> Ifeffit mailing list >>>> ifef...@millenia.cars.aps.anl.**__gov <mailto: >>>> ifef...@millenia.cars.**aps.anl.gov <Ifeffit@millenia.cars.aps.anl.gov> >>>> > >>>> http://millenia.cars.aps.anl._**_gov/mailman/listinfo/ifeffit < >>>> 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 >>>> ifef...@millenia.cars.aps.anl.**gov <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 >>> 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 >> > > > > -- > 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
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