[Ifeffit] Linear Combination Fitting using ATHENA

Teck Kwang Choo teck.kwang.choo at monash.edu
Tue Aug 13 23:20:18 CDT 2013


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.choo at 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 <mamarcus at 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 <mamarcus at lbl.gov <mailto:
>>> mamarcus at 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.
>>>
>>>
>>>
>>>
>>>
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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
>



-- 
Teck Kwang Choo
PhD Student
Department of Chemical Engineering
Room 225, Building 36
Monash University
Mobile No.: 04-11489904
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