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 Send Ifeffit mailing list submissions to ifeffit@millenia.cars.aps.anl.gov http://es.mc278.mail.yahoo.com/mc/compose?to=ifeffit@millenia.cars.aps.anl.g... To subscribe or unsubscribe via the World Wide Web, visit http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit or, via email, send a message with subject or body 'help' to ifeffit-request@millenia.cars.aps.anl.gov http://es.mc278.mail.yahoo.com/mc/compose?to=ifeffit-request@millenia.cars.a... You can reach the person managing the list at ifeffit-owner@millenia.cars.aps.anl.gov http://es.mc278.mail.yahoo.com/mc/compose?to=ifeffit-owner@millenia.cars.aps... When replying, please edit your Subject line so it is more specific than "Re: Contents of Ifeffit digest..." Today's Topics: 1. Re: Aligning Energy scales (Matt Newville) ---------------------------------------------------------------------- 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 Message-ID: http://es.mc278.mail.yahoo.com/mc/compose?to=K-Vb-0aRGwb9AC_W6BcBLwgCAg4t@ma... > Content-Type: text/plain; charset=ISO-8859-1 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 > > > > > _______________________________________________ > Ifeffit mailing list > Ifeffit@millenia.cars.aps.anl.gov http://es.mc278.mail.yahoo.com/mc/compose?to=Ifeffit@millenia.cars.aps.anl.g... > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit > > ------------------------------ _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://es.mc278.mail.yahoo.com/mc/compose?to=Ifeffit@millenia.cars.aps.anl.g... http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit End of Ifeffit Digest, Vol 91, Issue 28 *************************************** ns

Hi Elsa: As Matt suggested, you want to change E0 in Athena to produce a new chi(k) spectrum. You can read the theoretical chi(k) spectrum that you made with E0=0 into Athena, adjust E0 for the measurement, and then plot in k the data and theory to see them match at low k. I encourage you to poke around at the project files that I put at www.xafs.org/ShellyKelly. These project files show how to reproduce the relevant figures in the book chapter. Good luck, Shelly On Thu, Sep 30, 2010 at 10:33 AM, Elsa Sileo wrote:

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 < ifeffit-request@millenia.cars.aps.anl.gov>* escribió:

De: ifeffit-request@millenia.cars.aps.anl.gov < 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

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To: XAFS Analysis using Ifeffit http://es.mc278.mail.yahoo.com/mc/compose?to=ifeffit@millenia.cars.aps.anl.g...

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Subject: Re: [Ifeffit] Aligning Energy scales Message-ID: http://es.mc278.mail.yahoo.com/mc/compose?to=K-Vb-0aRGwb9AC_W6BcBLwgCAg4t@ma...

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Content-Type: text/plain; charset=ISO-8859-1

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

...

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

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: theoretical

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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.arhttp://es.mc278.mail.yahoo.com/mc/compose?to=sileo@qi.fcen.uba.ar

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End of Ifeffit Digest, Vol 91, Issue 28 ***************************************

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