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
To: XAFS Analysis using Ifeffit
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>>
Alexandre.
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Teck Kwang Choo
PhD Student
Department of Chemical Engineering
Room 225, Building 36
Monash University
Mobile No.: 04-11489904
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Teck Kwang Choo
PhD Student
Department of Chemical Engineering
Room 225, Building 36
Monash University
Mobile No.: 04-11489904
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Teck Kwang Choo
PhD Student
Department of Chemical Engineering
Room 225, Building 36
Monash University
Mobile No.: 04-11489904
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