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#dat... 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 ------------------------------------ bravel@bnl.gov 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/