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?
I've tried using Genplot, but that offers no way to restrain parametsrs to ranges to keep them from going nuts. PCA seems to want 6-8 components, so it's not all that helpful. These spectra were taken at various spots on a biological structure (abalone radula) so there's no sense of sequence which would enable the use of evolving factor analysis or something like that. LCF doesn't give satisfying fits with the references I have. I've attached a couple of the files, truncated to the range Manceau&Nagy fit to. The originas were taken over the range 2460-2550eV. mam
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2459.8232 0.0086620357 2460.0735 0.0090417974 2460.3235 0.033545561 2460.5737 0.0085842237 2460.824 0.0051017846 2461.074 0.011186908 2461.3242 0.017373042 2461.5742 0.015282798 2461.8245 0.020608777 2462.0747 0.030159647 2462.3247 0.037008617 2462.575 0.019812036 2462.825 0.017694598 2463.0752 0.021219229 2463.3252 0.025639383 2463.5754 0.022631068 2463.8257 0.014809187 2464.0757 0.016797649 2464.3259 0.020190042 2464.5759 0.015993463 2464.8262 0.023149636 2465.0764 0.025470076 2465.3264 0.019795895 2465.5767 0.026845468 2465.8267 0.018706912 2466.0769 0.033239357 2466.3269 0.034196496 2466.5771 0.025028745 2466.8274 0.034550779 2467.0774 0.039939508 2467.3276 0.025766766 2467.5776 0.042343114 2467.8279 0.023223488 2468.0779 0.048359003 2468.3281 0.040589523 2468.5784 0.043160751 2468.8284 0.051982671 2469.0786 0.059320733 2469.3286 0.077092245 2469.5789 0.065575883 2469.8289 0.082144961 2470.0784 0.070433557 2470.3281 0.084788643 2470.5779 0.10309343 2470.8274 0.11019815 2471.0771 0.13859501 2471.3269 0.19976343 2471.5767 0.25412217 2471.8264 0.34704304 2472.0759 0.54530066 2472.3257 0.78615826 2472.5754 1.0521393 2472.8252 1.2056561 2473.0747 1.3237689 2473.3245 1.4084748 2473.5742 1.4852122 2473.824 1.5177881 2474.0735 1.4640881 2474.3232 1.3413973 2474.573 1.1608815 2474.8228 1.008761 2475.0725 0.8627153 2475.322 0.85124922 2475.5718 0.86840338 2475.8213 0.90438408 2476.071 0.96190357 2476.3208 0.98449355 2476.5706 0.95443678 2476.8203 0.94638139 2477.0698 0.89626169 2477.3196 0.85532951 2477.5693 0.8831256 2477.8191 0.88665426 2478.0686 0.90146577 2478.3184 0.92120427 2478.5681 0.90238905 2478.8179 0.94114095 2479.0674 1.0159788 2479.3171 1.0523196 2479.5669 1.1367817 2479.8167 1.2791884 2480.0664 1.501315 2480.3159 1.8128476 2480.5657 2.2177896 2480.8152 2.4746833 2481.0649 2.6505656 2481.3147 2.7177446 2481.5645 2.7476342 2481.8142 2.9169872 2482.0637 3.0258553 2482.3135 3.2625239 2482.5632 3.2067261 2482.813 3.0880082 2483.0625 2.8586359 2483.3123 2.5289466 2483.562 2.2037165 2483.8118 1.9437176 2484.0613 1.7121388 2484.311 1.5392073 2484.5608 1.4665928 2484.8105 1.365666 2485.0603 1.2651333 2485.3098 1.2447017 2485.5596 1.2118043 2485.8091 1.1773263 2486.0588 1.1215008 2486.3086 1.1032519 2486.5583 1.0873834 2486.8081 1.0994042 2487.0576 1.100813 2487.3074 1.0825663 2487.5571 1.0809017 2487.8069 1.0712752
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