[Ifeffit] Athena: k-weight=3 in background removal problem

[Joseph Washington]

Greetings all,
I am an APS user and a graduate of XAFS Summer School - class of 2007 :) 
   We have been doing EXAFS analysis on Ge[2]Sb[2]Te[x] thin films. I 
noticed that at the Ge edge in particular, the k-weight value used in 
the background removal cannot equal 3, or else the background function 
no longer follows the data and oscillates wildly and/or it shoots up at 
the edge energy dominating the plot window. Values of 1 and 2 work fine. 
Even more puzzling is that this problem is inherent for the Ge edge of 
data taken over numerous runs, and for various samples (GST-224, 
GST-225, 226, 227).

Now if it is that the Ge-edge data is noisier than our Sb and Te edge 
data at higher k (I don't think this has been true), then in my opinion 
we should notice this at the Sb and Te edge data. So why the Ge-edge 
data? I want to point out that there are options that we have used, 
namely simply using a k-weight of 2, or specifying a spline clamp at 
high k that is "slight" or "weak". I just would like to know what lies 
at the root of this problem.

If further information is required, I would be happy to send you one of 
my project files showing some original scans collected for the Ge edge, 
as well as the merged Ge edge file.

Thank you very much,


-- 
Joseph Washington
Research Assistant
Department of Physics
North Carolina State University
431 Riddick Hall
Raleigh, NC 27695-8202
email: jswashin at ncsu.edu