[Ifeffit] Question about shift in E0

[Brandon Reese]

Hi all,

I am looking at EXAFS of thin film metal oxides.  I am varying both metal
content and the oxygen content of the films. I aligned the scans with a
metal reference foil collected simultaneously.  In Artemis, I have noticed
that when changing between films with no extra oxygen versus those with
extra oxygen there is a shift in the fitted E0 of ~1.5 eV (after aligning to
the foil). I tried setting the E0 in Athena to the peak of the 1st
derivative and the peak of the white line with the same result (~7 eV
difference). I was a little surprised by the offset because in Athena the E0
values varied by <0.5 eV. I am not sure if the argument could be made that
this shift is a result in a changing oxidation state because it doesn't show
up in the XANES (at least qualitatively).  Are there other experimental
effects that could cause a shift like this, or is this likely something real
in my material? If anyone want to see a representative group of data, let me
know.

I also have an unrelated quick (I think) question on the EXAFS equation. In
some references I see a term 1/(k R)^2 and in others it is 1/(k R^2). I
couldn't really see any reason for the difference, unless it is to correct
for subtle differences in how the other terms are defined.

Thanks
Brandon
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