On 07/18/2016 11:10 PM, Matthew Marcus wrote:
I'm trying to fit 37 micro-XANES spectra taken at the S K-edge, using
the method discussed in the paper by Manceau and Nagy "Quantitative
analysis of sulfur functional groups
in natural organic matter by XANES spectroscopy", Geochimica et
Cosmochimica Acta 99 (2012) 206–223. In this paper, they fit spectra to
two arctangents and 6 gaussians,
with widths of the arctans slaved together and widths of gaussians 1-3
and 4-6 slaved (or all 6 to one value). I'm looking for recommendations
as to how to do the fit.
They give prescriptions for how to set the initial estimates to give
robust values. Manceau has told me that 'Athena works quite well', but
I don't see any obvious way there
to do the parameter constraints called for, or to keep peak heights from
going negative. Athena also has a habit of assuming you want it to do
the normalization
for you; I've already done that and need no further 'help'. Any ideas?
Matthew,
As for the pre-normalized data, you are supposed to be able to tell
Athena at the time of import that the data are normalized mu(E).
http://bruceravel.github.io/demeter/documents/Athena/import/columns.html#data-types-and-energy-units
If that doesn't work, let me know.
As for constraints in the peak fitting, that is certainly not
implemented in Athena. I am not quite sure why Alain thinks otherwise.
HTH,
B
--
Bruce Ravel ------------------------------------ [email protected]
National Institute of Standards and Technology
Synchrotron Science Group at NSLS-II
Building 743, Room 114
Upton NY, 11973
Homepage: http://bruceravel.github.io/home/
Software: https://github.com/bruceravel
Demeter: http://bruceravel.github.io/demeter/
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