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"?
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