I completely agree with you, Jon. I did wonder about the small difference between the two plots I made after subtracting Z, which I presume now is the f(rel) in the reference you gave.
However, the precise values quoted for an element near an absorption edge have to be treated with care anyway given that oxidation state, etc. can change them. Hence, I wasn't so concerned about the small differences, but the big one which was due to Z (as per your reference) which is how I interpreted (or perhaps misunderstood) the original question. Your reference gives a better answer anyway. Cheers, Jeremy Karl. On 11 June 2015 at 17:07, Jonathan WRIGHT <wri...@esrf.fr> wrote: > Dear Xiaodong, Jeremy, > > Isn't it equation 3 here? > http://www.nist.gov/srd/upload/jpcrd488.pdf > f1/f2 are "dispersion" numbers and f'/f" are the "anomalous" ones. The > relativisitic correction number for iron then shows up on page 221. > > Best, > > Jon > === > > > On 11/06/2015 17:27, Jeremy Karl Cockcroft wrote: > > Hi Xiaodong, > I think that the numbers quoted for f' in the second case have had 26e > (atomic no.) added to them, i.e. it refers to the total dispersion value > for the real component (as opposed to the imaginary component). Given that > the numbers quoted are close to an absorption edge, then the remaining > differences are not unexpected depending on source and precise energy > quoted. If graphs of the data are plotted with Z subtracted, then they look > very similar apart from the precise value of the minimum of f' at the > absorption edge itself. > Just my thoughts on it... > Jeremy Karl. > *************************************************************** > Dr Jeremy Karl Cockcroft > Department of Chemistry > (University College London) > Christopher Ingold Laboratories > 20 Gordon Street > London WC1H 0AJ > United Kingdom > +44 (0) 20 7679 1004 (laboratory) > j.k.cockcr...@ucl.ac.uk or jeremyk...@gmail.com > http://img.chem.ucl.ac.uk/www/cockcroft/homepage.htm > *************************************************************** > > > On 11 June 2015 at 15:33, iangie <ian...@126.com> wrote: > >> Dear Rietvelders, >> >> I am little confused about the term "Anomalous scattering factor" and >> "Dispersion coefficients". >> "Anomalous scattering factor" can be found here >> http://skuld.bmsc.washington.edu/scatter/AS_form.html >> "Dispersion coefficients" can be found here >> http://www.cxro.lbl.gov/optical_constants/asf.html >> >> Their numbers are quite different: e.g. Fe @ CrKα: f0=18.474, Δf'=-1.6 >> Δf"=0.9 >> ; however, the corresponding dispersion coefficients are f' ~24.6808 and >> f" ~0.759346 >> Can anyone explain their relationship? >> >> Thanks! >> -- >> Yours Sincerely, >> Dr. Xiaodong(Tony) Wang >> XRD Application Scientist >> Bruker Singapore Pte. Ltd. >> >> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ >> Please do NOT attach files to the whole list >> <alan.he...@neutronoptics.com> <alan.he...@neutronoptics.com> >> Send commands to <lists...@ill.fr> eg: HELP as the subject with no body >> text >> The Rietveld_L list archive is on >> http://www.mail-archive.com/rietveld_l@ill.fr/ >> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ >> >> >> > > > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > Please do NOT attach files to the whole list <alan.he...@neutronoptics.com > > > Send commands to <lists...@ill.fr> eg: HELP as the subject with no body > text > The Rietveld_L list archive is on > http://www.mail-archive.com/rietveld_l@ill.fr/ > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > >
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