[Ifeffit] Athena: problems with LCF

[Nina Siebers]

Dear All,

I acquired Cd L3-edge spectra of some binary and ternary mixtures in  
varying proportions and for the individual components. The mixtures  
were created on Cd-mass basis. Then, I tried to fit the reference  
spectra to the spectra of the mixtures using linear combination  
fitting of Athena to get their abundance. However, the results were  
disappointing despite all spectra were carefully energy calibrated and  
normalized, so I decided to create simple mathematical binary and  
ternary mixtures by summing up the spectra of the individual reference  
spectra. After that I did an edge-step normalization in excel and  
imported the normalized calculated mixtures into Athena. Then, I tried  
the fitting again to exclude mixing-failures and check sensitivity of  
LCF with the idealized spectra. Even though the results of the LCF of  
the mathematical mixtures were better compared to the real mixtures,  
LCF was also not able to reliable deconvolute these spectra into the  
individual reference spectra.

Does anybody have an explanation for that? It would be nice if  
somebody could give me information about the mathematical fitting  
algorithm implemented in Athena.

Attached is a data file of three mixtures (two ternary and one binary  
mixture) including the mathematical mixture created in excel (named  
calculated at the end). Mixing ratios are named 1to1to1 (meaning 1:1:1  
of the components in the same order). For the 1:1:1 ternary  
mathematical mixture the deconvolution was very good, but the others  
need improvement.

I hope I made my problem clear this time.

Thanks a lot!
Wishes,
Nina


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