Re: [Ifeffit] Ifeffit Digest, Vol 104, Issue 22

Julian: I agree with Anatoly. The amplitude of the EXAFS is quite large. I have seen a similar effect in metal foils and NP samples when you forget to take the log of the I0 and IT. This also forces the S02 factor to be artificially high (like it is for your samples) when fitting in Artemis. Maybe try to re-adjust the raw data file upon importing into Athena and then see if your spectra (intensities, features and S02) line up better with those from the literature (and from the very useful Lytle database on XAFS.org). Hope that helps Dave On Fri, Oct 14, 2011 at 9:14 AM, wrote:

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Today's Topics:

1. Re: Gold Nanoparticle first shell fitting (Kaiser, Julian)

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Message: 1 Date: Fri, 14 Oct 2011 14:14:00 +0000 From: "Kaiser, Julian" To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] Gold Nanoparticle first shell fitting Message-ID: Content-Type: text/plain; charset="iso-8859-1"

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@millenia.cars.aps.anl.gov [ ifeffit-bounces@millenia.cars.aps.anl.gov]" im Auftrag von "Anatoly I Frenkel [afrenke2@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@millenia.cars.aps.anl.gov [ ifeffit-bounces@millenia.cars.aps.anl.gov] on behalf of Kaiser, Julian [ julian.kaiser@helmholtz-berlin.de] Sent: Tuesday, October 11, 2011 1:06 PM To: ifeffit@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 Angstr?m 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 f?r 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 Gesch?ftsf?hrer: 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