Thanks for the quick answer Bruce. I'll definetely take into account your point on the pre and post edge ranges and I will check if it makes any changes in the normalization next time I go to APS (in a few days actually). Going back to the original question, I did select 8 standards for both cases (single fit with "fit this group" and combination of fits with "fit all combinations"), which gives me 247 combinations (see Excel file attached). In the case of the single fit I get a R-factor of 2.0x10-3 whereas for the best fit from the combinations I got 1.8x10-3 (the weights of each standards are also different in both cases). I selected the whole range of the spectrum for the fit and forced the weights to be equal to 1. The 8 standards are put in the following order in the library: Fe3O4(4), Pure Fe2O3, SM Fe in pure Zr metal, SM Fe in Zr-4 SPP, SM SA Fe in Zr-4 matrix, Fe3O4(2), Fe2O3(4), Pure Fe (4). I hope this is enough information for you to reproduce what I am doing. Thanks again, -- Adrien Couet Graduate Student Dept of Nuclear Engineering, Penn State University +1 814 865 9709 axc1019@psu.edu