Hi Nathan: The peaks you see are pretty typical when you start at E0 and have the edge jump and a significant white line and it attempted to be "fit" to a smooth backgorund. Since your FT window starts at least at k=2A, all of these wild oscillations are not a factor. The important thing is that your FT is reasonable and that when you plot the weighted Chi(k) it looks relatively decent. In short, you are usually OK with the default parameters Carlo On Mon, 18 Mar 2019, Nathan Nakamura wrote:

Hello,

I am working on some data processing of ZrO2 thin films collected in fluorescence mode, and had a question regarding the background subtraction in Athena. When I use the default values, I see a large negative spike in the background curve (shown in BGsubtract1.png). I can vary the spline clamps and other parameters to reduce this (BGsubtract1.copy), but it does not seem to have any significant effect on the final EXAFS (EXAFScompare.png).

My question is, do large spikes/instabilities on the edge like this need to be accounted for, or are they ok as long as the background fit after the edge seems fine? My thought is that as long as the EXAFS is not significantly affected, it should be fine, but I do not have a good sense for how the presence of this peak may impact the background curve beyond the absorption edge. I have also attached the project file in Athena for reference.

Thanks, -Nathan

-- Carlo U. Segre -- Duchossois Leadership Professor of Physics Interim Chair, Department of Chemistry Director, Center for Synchrotron Radiation Research and Instrumentation Illinois Institute of Technology Voice: 312.567.3498 Fax: 312.567.3494 segre@iit.edu http://phys.iit.edu/~segre segre@debian.org