[Ifeffit] Gold Nanoparticle first shell fitting

[Anatoly I Frenkel]

Dear Julian,



I should've guessed earlier, but now I see that the only reason is that you did not take natural log when you constructed your transmission EXAFS signal from detector data. I assume it is transmission since your group name says so.

It explains all problems with your data in the foil, and the NP fit, weird looking XANES and wrong S02.



And, by the way, the differences between the two synchrotrons is acctually huge, especially in the XANES, but it is hard to discuss differences in the signals that are exp(mu) instead of mu.



Anatoly

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From: ifeffit-bounces at millenia.cars.aps.anl.gov [ifeffit-bounces at millenia.cars.aps.anl.gov] on behalf of Kaiser, Julian [julian.kaiser at helmholtz-berlin.de]
Sent: Friday, October 14, 2011 10:14 AM
To: XAFS Analysis using Ifeffit
Subject: Re: [Ifeffit] Gold Nanoparticle first shell fitting

Dear Anatoly,

thanks a lot for your reply!
I don't see the problem yet. In the attached file ("different_Au_foils.prj), there are two different gold reference foils measured at two different synchrotrons. There is some difference but not realy much. Could you please describe the regions that are worse comparing my gold foil-file to yours, or if possible, attache the file with both foils or at least a screenshot of the plot?

Best regards,
Julian



________________________________
Von: ifeffit-bounces at millenia.cars.aps.anl.gov [ifeffit-bounces at millenia.cars.aps.anl.gov]" im Auftrag von "Anatoly I Frenkel [afrenke2 at yu.edu]
Gesendet: Dienstag, 11. Oktober 2011 20:29
Bis: XAFS Analysis using Ifeffit
Betreff: Re: [Ifeffit] Gold Nanoparticle first shell fitting


Something is horribly wrong with the data here.

I overplotted your reference Au foil against mine, and yours has distorted XANES and too high EXAFS intensity compared to my data. Your amplitude factor is 1.54 which also confirms that something was wrong in the experiment. Perhaps - a misalignment? The NP data also look strange...

I would not focus on the NP analysis until you figure out why your foil data is so strange.





________________________________
From: ifeffit-bounces at millenia.cars.aps.anl.gov [ifeffit-bounces at millenia.cars.aps.anl.gov] on behalf of Kaiser, Julian [julian.kaiser at helmholtz-berlin.de]
Sent: Tuesday, October 11, 2011 1:06 PM
To: ifeffit at millenia.cars.aps.anl.gov
Subject: [Ifeffit] Gold Nanoparticle first shell fitting

Dear Ifeffit Community,

I'm trying to fit a gold nanoparticle in the size of about 2 nm that is immobilized by polymers. For my research it's enought to fit the first shell only, becaues all I would like to analyze is the atomic distance in the nanoparticle. After the (hopefully) correct background substraction in Athena (athena file attached), there is a shoulder at approx. 2.1 Angström in the R-space.
In Artemis, fitting this shoulder seems not to be possible, while the fit for the reference (gold foil) seems to be fine. (both artemis files are attached to the e-mail).
If the k-range is decreased from 12.388 to a value between 9 an 10, the shoulder disappears and the fit works fine. But I think by this change I might modify the data too much.
Would be really nice, if sombody has an idea how to deal with the problem, to get a hint how to solve this.

Thanks a lot,
Julian

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________________________________

Helmholtz-Zentrum Berlin für Materialien und Energie GmbH

Mitglied der Hermann von Helmholtz-Gemeinschaft Deutscher Forschungszentren e.V.

Aufsichtsrat: Vorsitzender Prof. Dr. Dr. h.c. mult. Joachim Treusch, stv. Vorsitzende Dr. Beatrix Vierkorn-Rudolph
Geschäftsführer: Prof. Dr. Anke Rita Kaysser-Pyzalla, Dr. Ulrich Breuer

Sitz Berlin, AG Charlottenburg, 89 HRB 5583

Postadresse:
Hahn-Meitner-Platz 1
D-14109 Berlin

http://www.helmholtz-berlin.de
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