It is because you made delta E0=0, but the fit gave you delta E0=8. Since the fit agrees with the data in k-space at low wavenumbers (I assume), then the signal with delta E0=0 should not, and vice versa.
Anatoly
________________________________
From: ifeffit-bounces@millenia.cars.aps.anl.gov on behalf of Elsa Sileo
Sent: Thu 9/30/2010 11:33 AM
To: ifeffit@millenia.cars.aps.anl.gov
Subject: Re: [Ifeffit] Ifeffit Digest, Vol 91, Issue 28
Dear Matt,
I have to perform EXAFS analysis, and when I tried to fit the first shell, I found deltaE0 values of about 8 eV. Following the paper of Kelly et al (Analysis of soils and minerals using X-ray absorption spectroscopy. In Methods of soil analysis, Part 5: Mineralogical methods; 2008; pp 446) I fitted the first shell obtaining values for deltaE0, sigma^2; delta R and amplitude. Then, using the obtained values, and making deltaE0=0, I got the theoretical signal.
When I compare the experimental and theoretical spectrum I see a mismatch between the position of the nodes at low wavenumbers.
Having done this, how I have to proceed to correct the experimental data in order to obtain smalller delta E0 values?
Thanks in advance,
Elsa
--- El mié, 29/9/10, ifeffit-request@millenia.cars.aps.anl.gov escribió:
De: ifeffit-request@millenia.cars.aps.anl.gov
Asunto: Ifeffit Digest, Vol 91, Issue 28
Para: ifeffit@millenia.cars.aps.anl.gov
Fecha: miércoles, 29 de septiembre, 2010 14:00
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Today's Topics:
1. Re: Aligning Energy scales (Matt Newville)
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Message: 1
Date: Tue, 28 Sep 2010 12:55:15 -0500
From: Matt Newville http://es.mc278.mail.yahoo.com/mc/compose?to=newville@cars.uchicago.edu >
To: XAFS Analysis using Ifeffit http://es.mc278.mail.yahoo.com/mc/compose?to=ifeffit@millenia.cars.aps.anl.g... >
Subject: Re: [Ifeffit] Aligning Energy scales
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Dear Elsa,
It sounds like you want to adjust the data chi(k) so that deltaE0 is 0
in a fit. Is that correct, or are you trying to do something else
(say, align the XANES)? If that assumption is correct, you want to
change the E0 used to extract chi(k) from the experimental spectra --
the E0 of the background subtraction. That is what sets k for the
data.
If that's not clear or not the right question, let us know,
--Matt
On Mon, Sep 27, 2010 at 2:00 PM, Elsa E. Sileo http://es.mc278.mail.yahoo.com/mc/compose?to=sileo@qi.fcen.uba.ar > wrote:
> I need to align a measured spectra to a theoretically calculated spectra.
> I fitted the first shell obtaining values for deltaE0, sigma^2; delta R and
> amplitude.
> Then, using the obtained values, and making deltaE0=0, I got the theoretical
> signal.
> But I do not know how to use this last theoretical fit to align the spectra.
> Can somebody help me?
>
> Thanks,
>
> Elsa
>
>
> Dra. Elsa E. Sileo
> Solidos Inorganicos
> INQUIMAE - Dto. Qca. Inorganica, Analitica y Qca. Fisica; FCEN, UBA
> Int. G?iraldes 2160, Pabell?n 2, Piso 3, Ciudad Universitaria - C1428EHA
> CABA - Argentina
> Tel: (54 11) 4576 3380 ext. 113
> Fax: (54 11) 4576 3341
> e-mail: sileo@qi.fcen.uba.ar http://es.mc278.mail.yahoo.com/mc/compose?to=sileo@qi.fcen.uba.ar
>
>
>
>
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