Dear Edmund,
Thanks for your explain. But I am still puzzled. Following your instruction, I performed Self-Absorption for the samples, choosing XANES(Fluo) from algorithm, but I did not know the real meaning of Formula. Does it mean the species formula which I wish to detect? Or the whole composition of the sample? I used natural mineral to interact with selenite, then I wish to check the speciation of the selenium reaction product. For my case, should I fill the blank with Se or FeSe or both of them (because currently I do not know the exactly containing speciation)? For the angles, normally are they 45? Becuase I measured the samples in fluorescence mode, and didnot measure the angles between sample, incoming beam and detector. I tried to input Se in the Formula entry, and select 45 for the angles, then I got a corrected spectra which was higher than the original one. But when I using this spectra for LCF analysis, I still could not got overlapping line for the fitted spectra with the sample spectra...Wish to obtain more information from you. Thanks very much.
Best wishes
Mingliang
在2010-01-29 00:37:41，"Welter, Edmund" <edmund.welter@desy.de> 写道： >Dear Mingliang, > >simply because Athena is not normalising the height of the highest peak >(the white line) but the EXAFS region, that is it starts some 10 eV >above the edge. You choose the normalisation region in Athenas settings. > You can see in your plots that it does this job quite well, the >spectra oscillate around 1 (at E > E0+40 eV). > >Anyway, take care what you do when you try to fit a fluorescence yield >XAFS spectrum with references which were measured in transmission mode. >You must at least be sure that you considered the "self absorption >effect" which dampens the oscillations (most notably the large >oscillations in the XANES region). The importance of this effect depends >on your sample's composition. > >Athena contains functions to correct the self absorption. In order to do >this you need the elemental composition of your sample and the angles >between sample, incoming beam and detector. > >Best regards, >Edmund Welter > >康明亮 wrote: >> Dear, >> I want to to ask a question about using Linear Combination Fitting in >> Athena. I normalized all the references(measured in transmission mode) >> and samples (fuorescence mode) with Athena, and then wish to use LCF to >> quantify each unique component in the samples. But I noted that the >> normalized samples spectra had lower height at the white line peak than >> any references(shown pic-1.emf in annex), thus the fitted spectra >> were also higher than the original sample spectra (shown pic-2 and >> -3.emf in annex). I do not know why? I also attached all the original >> data(before normalization). Wish to obtain guidance from you. Thanks! >> Best wishes >> Mingliang >> >> >> ------------------------------------------------------------------------ >> 网易邮箱，没有垃圾邮件的免费电子邮箱！ <http://www.yeah.net/?from=o1> >> ------------------------------------------------------------------------ >> >> >> ------------------------------------------------------------------------ >> >> >> ------------------------------------------------------------------------ >> >> >> ------------------------------------------------------------------------ >> >> >> ------------------------------------------------------------------------ >> >> >> ------------------------------------------------------------------------ >> >> _______________________________________________ >> Ifeffit mailing list >> Ifeffit@millenia.cars.aps.anl.gov >> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit