Hi Dominik,
Thank you so much for your quick response. Indeed, it's really nice fitting according to your result. But my situation seems a little bit different as I'm dealing with the Mn XANES data and there're doublets and sometimes triplets in the pre-edge. Actually, I might as well explain my interest of doing such fitting. I read in the paper (F Farges, PHYSICAL REVIEW B 71, 155109 (2005)) that the centroid of pre-edge peak is a more accurate measurement of the oxidation state of the element of interest, compared to the more conventional inflection point or half-way method. So I was trying to follow the paper and see if it also works for my samples. Anyway, thanks again for your help!
Enyuan
On Thu, Aug 9, 2012 at 9:11 AM,
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Today's Topics:
1. Re: question for ifeffit mailing list - ATHENA NORMALIZATION
(Marie Zwetsloot)
2. Re: question for ifeffit mailing list - ATHENA NORMALIZATION
(Scott Calvin)
3. pre-edge centroid (Enyuan Hu)
4. Re: pre-edge centroid (Dominik Samuelis)
----------------------------------------------------------------------
Message: 1
Date: Wed, 8 Aug 2012 13:17:59 -0400
From: Marie Zwetsloot <mjz56@cornell.edu>
To: ifeffit@millenia.cars.aps.anl.gov
Subject: Re: [Ifeffit] question for ifeffit mailing list - ATHENA
NORMALIZATION
Message-ID:
<CALtZdD54=1-w4U3vk7DdNU_CUkGpK-1vJ3ioOR_CSvkj4UeCXw@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Hi Scott Calvin,
Thanks for your help. Yes, this is as far as my pre- and post-edge range
go. I realized I should have made them longer; it was my first time doing
this and wasnt aware that i should lengthen my pre and post-edge for later
on analysis. This will be good lesson for the future.
So you would not recommend doing linear combination fitting? I was planning
on trying it out.. But I wouldnt want to do it if with my pre- and
post-edge range, I am bound to derive wrong conclusions from the data.
Best,
Marie
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Message: 2
Date: Wed, 8 Aug 2012 15:10:16 -0400
From: Scott Calvin <scalvin@sarahlawrence.edu>
To: XAFS Analysis using Ifeffit <ifeffit@millenia.cars.aps.anl.gov>
Subject: Re: [Ifeffit] question for ifeffit mailing list - ATHENA
NORMALIZATION
Message-ID: <B36E3403-35BC-48BE-8E4D-AE2CB8556769@slc.edu>
Content-Type: text/plain; charset="iso-8859-1"
Hi Marie,
I think you can try linear combination fitting, but you'll have to build in the uncertainty in normalization in to your own estimates of uncertainty.
If you don't check the box that says "force weights to sum to 1," then you can allow for normalization errors in your sample.
If your standards also have only short energy ranges, then there's nothing you can do about that, though. As I said, you'll just have to build them in to your uncertainty. If you are unsure of the edge jump of a standard to 20%, then the contribution of that standard to the linear combination fit is uncertain by 20%.
Uncertainty in normalization is one of the leading contributions to the uncertainty that should be associated with linear combination fitting, even when the energy ranges are sufficient. In a case like yours, they're bigger than they could have been, but it doesn't mean you can't use linear combination analysis at all.
--Scott Calvin
Sarah Lawrence College
On Aug 8, 2012, at 1:17 PM, Marie Zwetsloot wrote:
> Hi Scott Calvin,
>
> Thanks for your help. Yes, this is as far as my pre- and post-edge range go. I realized I should have made them longer; it was my first time doing this and wasnt aware that i should lengthen my pre and post-edge for later on analysis. This will be good lesson for the future.
>
> So you would not recommend doing linear combination fitting? I was planning on trying it out.. But I wouldnt want to do it if with my pre- and post-edge range, I am bound to derive wrong conclusions from the data.
>
> Best,
> Marie
> _______________________________________________
> Ifeffit mailing list
> Ifeffit@millenia.cars.aps.anl.gov
> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
------------------------------
Message: 3
Date: Thu, 9 Aug 2012 00:21:14 -0400
From: Enyuan Hu <bearcharge@gmail.com>
To: ifeffit <ifeffit@millenia.cars.aps.anl.gov>
Subject: [Ifeffit] pre-edge centroid
Message-ID:
<CAJud35NRYb67J7xLATPHPJGjEyvOK_gUKZur+dL9T30x8k=UHA@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Dear all,
I was wondering if anyone could comment on how to get the centroid of
pre-edge by fitting the pre-edge peak by pseudo-Voigt functions. I tried to
do that in Athena, but it seemed that peaking fitting part is the
relatively less developed function in the software. Any comment would be
appreciated.
Enyuan
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Message: 4
Date: Thu, 09 Aug 2012 15:11:31 +0200
From: Dominik Samuelis <d.samuelis@fkf.mpg.de>
To: XAFS Analysis using Ifeffit <ifeffit@millenia.cars.aps.anl.gov>
Subject: Re: [Ifeffit] pre-edge centroid
Message-ID: <5023B703.6020609@fkf.mpg.de>
Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
Dear Enyuan,
in my experience, peak fitting works very well with Athena. Try not to
fit only the prepeak, but maybe include an arctan describing the edge
(see attached pdf, the fit was made using athena). This makes isolating
the prepeak much more reliable.
Best regards,
Dominik
On 09.08.2012 06:21, Enyuan Hu wrote:
> Dear all,
>
> I was wondering if anyone could comment on how to get the centroid of
> pre-edge by fitting the pre-edge peak by pseudo-Voigt functions. I tried
> to do that in Athena, but it seemed that peaking fitting part is the
> relatively less developed function in the software. Any comment would be
> appreciated.
>
> Enyuan
>
>
> _______________________________________________
> Ifeffit mailing list
> Ifeffit@millenia.cars.aps.anl.gov
> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>
--
Dr. Dominik Samuelis
d.samuelis@fkf.mpg.de
Max-Planck-Institut f?r Festk?rperforschung
Max Planck Institute for Solid State Research
Heisenbergstr. 1
70569 Stuttgart
Germany
Phone +49-711-689-1769
Fax +49-711-689-1722
Web http://www.fkf.mpg.de/maier/
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