[Ifeffit] Shift in Eo when fitting PtO2 and similar samples

[Kelly, Shelly Diane]

Hello Yanny:

I've modeled a few Pt EXAFS spectra and have found that using an E0 at the top of the white line usually does a better job of getting the data close to the theory. This seems to be often the case with the L3-edges as they are rather broad compared to the K-edges of transition metals.  If you would like to share your project files with me. I can take a look.  14 eV seems to be too much and maybe an indication that there is a different type of atom in the first shell.

B.T.W. Using the first derivative is great for XANES analysis, but often not the best choice for EXAFS.

Kind regards,
Shelly Kelly (skelly at anl.gov)

From: Ifeffit <ifeffit-bounces at millenia.cars.aps.anl.gov> On Behalf Of Zi Qi Chen
Sent: Tuesday, August 22, 2023 9:53 AM
To: ifeffit at millenia.cars.aps.anl.gov
Subject: [Ifeffit] Shift in Eo when fitting PtO2 and similar samples

Dear all,

I am looking at EXAFS of PtO2 powders and Pt particles supported on TiO2. I used a beta-PtO2 crystal structure data for the PtO2 EXAFS and after the first shell fit, I observed a large shift in Eo (delta Eo of ~14 eV) in my fit parameters. When I tried to fit the Pt foil to obtain the So2, the energy shift also seemed high (delta Eo of ~7 eV). I am wondering if there could be a problem in the selection of Eo prior to EXAFS analysis? I left the Eo as the energy at the first peak of first derivative (ifeffit default).
All of the data were also aligned using the reference foil in Athena before looking at EXAFS. I am wondering what would have caused this shift? Any help is appreciated, thank you.

Best regards,
Yanny

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