[Ifeffit] Very large exafs amplitude in collected data - cause unknown

Daniel Olive dolive at lbl.gov
Wed Jun 5 13:18:00 CDT 2013

Hi All,

Well, this is certainly interesting. I had a chance to look at the data myself, and although I can't say if the results are meaningful, or useful, or even what you wanted, I don't see large amplitudes like Jason and Bruce report. 

A quick glance at the header of the files showed a list of column heading. Column 1 was energy. No I0, but, there was a counter, and everything else was DXP related so I guessed that was your ion chamber. DXP_Total caught my eye, and I'm guessing it sums the dxp## columns that follow. I loaded column 1 vs. (8/7) in Athena. I had to change all the groups to Au L3 edge, and I fixed the E0 to something sensible like 11923 (it's default position was somewhere after the white line). After changing the pre-edge range so it didn't end so close to the peak (-182 to -90) I merged them. k2 weighted graph attached.

A quick first shell fit in Artemis gave me something like 15 Au neighbors at around the distance predicted in, 
The plot even looks kind of like their data. (Disclaimer: this was by no means a proper fit, but not bad for 2 minutes and a google search).

So...It may not be as hopeless as you think. Without knowing anything about the samples or the experimental setup, you may still need to look into dead time correction, self-absorption correction, etc., and by all means look at each detector channel and make sure you're not summing in bad channels. I can't agree strongly enough with the need to look at the data as it comes in (it's a lesson I suspect many of us learned the hard way at some point), and Jason, welcome to the list.


Daniel Olive     ---     dolive at lbl.gov
Postdoctoral Researcher
University of California, Berkeley

Nuclear Science Division
Lawrence Berkeley National Laboratory
1 Cyclotron Road
MS 70A1150, Room 70A-2205B
Berkeley, CA 94720-8175

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20130605/94045bcb/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: athena.png
Type: image/png
Size: 9884 bytes
Desc: not available
URL: <http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20130605/94045bcb/attachment.png>

More information about the Ifeffit mailing list