Dear Fred,
Thank you for the quick answer. Which range should I have for the EXAFS analysis to be meaningful? Like 200eV above the edge?
Thanks again,
Irina.
________________________________
From: Ifeffit on behalf of fred.mosselmans@diamond.ac.uk
Sent: 06 September 2016 03:27:43
To: ifeffit@millenia.cars.aps.anl.gov
Subject: Re: [Ifeffit] Help in background removal with Athena
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From: Ifeffit [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of ifeffit-request@millenia.cars.aps.anl.gov
Sent: 06 September 2016 14:57
To: ifeffit@millenia.cars.aps.anl.gov
Subject: Ifeffit Digest, Vol 163, Issue 6
Dear Irina,
Your efforts are probably sadly in vain. C K-edge NEXAFS or XANES is common, but the data range is rarely long enough for exafs analysis. You have ca 160 eV of data that is not enough for EXAFS analysis. Hence I don't think there is a way to get a good background and then FT for your data. Certainly looking at your data the noise level and thus uncertainty in which features are real and which may not be will probably prevent anything but a XANES analysis. There probably is an oscillation there but with the limited data range getting meaningful numbers from a fit is most unlikely.
Best wishes
Fred
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Today's Topics:
1. Help in background removal with Athena (Irina Pi)
----------------------------------------------------------------------
Message: 1
Date: Tue, 6 Sep 2016 13:56:19 +0000
From: Irina Pi
To: "ifeffit@millenia.cars.aps.anl.gov"
Subject: [Ifeffit] Help in background removal with Athena
Message-ID:
Content-Type: text/plain; charset="iso-8859-1"
Dear all,
I am sorry to bother you with my tiny problems, but I have been struggling with it for a long time. The thing is I have XAS data from a graphite sample, and I don't know if I'm plotting the background correctly in it with Athena software, which determines a lot the response in the Fourier transform, and thus in our results.
I'm attaching the data as data_exafs.txt, and also two different Athena projects of different backgrount fittings, graphite_exafs1.prj and graphite_exafs2.prj. Just in case projects cannot be seen, I'm also attaching screenshots (1-01deg.png and 2-01deg.png) of the different background fittings and the parameters used in Athena in only one set of data (01deg), because they are the same in the others (02deg and 35deg). Also, the final R-space plot in both fittings are sent (1-rspace.pdf and 2-rspace.pdf).
What I wanted to ask is why it is so different the result according to the background removal. And are they correct the fittings I've done?
I would like to have a background line similar to the other figure attached (0deg.pdf, but take into account that it is from different data), but I cannot get it. I guess this last fitting seems better, doesn't it?
What could I do to have good results in the Fourier transform?
Again, sorry but I don't have much experience and it seems to be so subjective that I fear doing it all wrong.
Thank you very much,
Best regards,
Irina Pi Jauma.
