In checking the literature, has anyone indicated what data collection
ranges they used, and what pre- and post-edge
regions were selected for normalisation?
Do you have more data below 2800eV that you are not showing?
Starting data collection only 50 eV or so below the edge can be
problematic for estimating background,
particularly so if a large feature (white line) is present at the edge.
Around 2810 eV, the step size has changed from coarser to finer steps in
energy:
and that seems to be associated with a change in slope, but with more
noise in the coarser step range.
If I had to pick something with just this data, I could tolerate using
the first 10 eV of the scan for
the pre-edge...
If it is just this one sample, and you aren't trying to conclude
anything from absolute intensities,
this could be reasonable. If you are comparing, be consistent in how you
treat the data, and understand
(and admit in presenting the data) that there can be errors associated
with normalisation.
If I vary the post-edge values a few eV to either direction, the edge
step changes by +/- 0.03 (0.90+/-0.03).
The variation is even larger if I push the pre-edge upper limit to
closer to the edge. (and I can convince myself
that the 1st ~15 eV of the scan are reasonable, for an edge step closer
to 0.94)
Generally, for this and future reference, make sure you have sufficient
data range for processing. This
will vary depending on what edge you are studying, but here, I would
have started at least 100 eV below
the edge.
Understand that processing has an element of subjective interpretation
to it - asking yourself what is reasonable.
Treat similar data consistently.
Probably paraphrasing Bruce a bit, but he has a mantra of "Data handling
and interpretation should be done
in a manner that is reasonable, plausible, and defensible." Over time,
through experience, you can gain
an understanding of what constitutes reasonable, plausible and
defensible. Practice on some standards
at different edges to get a feel for it.
Some more unsolicited advice:
Avoid bias - let the data tell their story. Explain how the data were
collected. Describe in detail how the spectra
were processed. Discuss the results - what you observe, how it compares
to literature. If you see differences,
report differences, and consider what might be plausible explanations.
On 2020-12-07 8:55 a.m., Deka, N. wrote:
Dear all
I am a student trying to learn Athena for XAS data processing.
Attached is a data file which contains L3 and L2 edge of Ru. What
should be the right parameters for background removal and
normalization of this data set? In the videos from Bruce Ravel, I
could not find any example for such a data set containing two edges.
Thank you
Best Regards,
Nipon Deka
Leiden University
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