Dear Matt and dear all,
I have encountered an issue processing oversampled EXAFS data with 
Larch. In my example the energy step is 0.33 eV in all parts of the 
scan, including the EXAFS. When I use the default procedure in Larch 
(pre_edge and then autobk), I get the noise level in chi(k) that is 
higher than I would expect.  Strangely, rebinning of mu(E) using 
rebin_xafs function does not help, and even increases the noise. The 
lowest level of noise can be obtained when rebinning the data in k 
(starting from the "raw" oversampled chi(E) provided by Larch). In this 
last case, the result is noise-wise very similar to Athena's default.

I think that the high level of noise after the default Larch processing 
can be due to the fact that Larch does not seem to do averaging when 
converting the data from E to k. Instead, it does interpolation with 
UnivariateSpline which by design is not supposed to decrease the noise 
when applied to oversampled data. Is this correct? Would it be worth 
changing?

The reason why the rebinning in E does not decrease the noise is not 
clear to me. Do you have any idea?

Has anyone run into similar issues? Any comments and suggestions are 
welcome.

In case you might want to investigate, I attach a picture that 
summarizes the results and a file with the mu(E) data.

Thank you

Best regards,
Kirill Lomachenko

-- 
Dr. Kirill A. Lomachenko
Scientist at BM23/ID24 beamlines
European Synchrotron Radiation Facility
71 avenue des Martyrs
CS 40220
38043 Grenoble Cedex 9, France
Tel: +33 438 88 19 14
https://urldefense.us/v3/__http://www.esrf.eu__;!!G_uCfscf7eWS!d68Np3QntexDZYvBniYfHaapxXKJl1bBclM3IMx2t57i1Hn-sCFmZBJiBCVWYn4I1HDXtMGdrsVFkSDstBxUmo-DiAcV1B8B6Q$