[Ifeffit] Ifeffit Digest, Vol 158, Issue 3

Matt Newville newville at cars.uchicago.edu
Sun Apr 3 21:04:58 CDT 2016


Hi Matthew,



On Sun, Apr 3, 2016 at 8:13 PM, Matthew Marcus <mamarcus at lbl.gov> wrote:

> <Rant>
> It shouldn't be called 'self-absorption'.  That's a misnomer, which seems
> to have come from a 1992
> paper (Troger, et. al."Full correction of the self-absorption in
> soft-fluorescence extended x-ray-absorption fine structure", PRB 46,3283
> (1992).
> The effect was described and analyzed in a 1982 paper, which called it an
> "attenuation factor": Goulon, et. al. "On experimental attenuation factors
> of the amplitude
> of the EXAFS oscillations in absorption, reflectivity and luminescence
> measurements", J. Physique 43, 539 (1982).
> </Rant>
>         mam
>
>
Thanks!! I completely agree, though I wasn't aware of the historical
precedence for the mistake.    Using "over-absorption" is a far better
term.

In X-ray fluorescence,  "self-absorption" actually means the attenuation of
fluorescence generated within a sample as it travels out of the sample.
For over-absorption in XAFS, the issue is measuring absorption in
fluorescence mode when the concentration of the absorbing element is not
infinitesimal or when the sample thickness is not infinitesimal.

--Matt
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