[Ifeffit] Hephaestus: Absorption Data Source

[Daniel Przyrembel]

Hi Bruce

Thank you very much for your reply: It is a relief to know I have been
looking in the wrong place only and that I am not blind or illiterate.

I already thought that, assuming the data source was Keski-Rahkonen &
Krause, the values were not precise, but accurate. And that is perfectly
fine with me, I just need to know e.g. whether the natural line width of
Au 4f7/2 is 0.22eV or 0.30eV, not whether it's 0.220eV or 0.216eV.

As a side note: Basic things like these seem to be just not intriguing
enough for anyone to look into elaborately nowadays and that is why
whenever one feels the urge to find out, we eventually end up at browsing
publications from roughly the second half of the 20th century and reading
off values from - sometimes coarsely - printed graphs or interpolating
somewhat rough data points (I've had a go myself recently at theoretical
photoisomerization cross sections and asymmetry parameters already...).
And that is why many people tend to use and take for granted the same
tabulated values - sometimes for decades even though they turn out to be
not quite correct in the end...

Anyway, I'm happy to know now where the core-hole linewidth values in
Hephaestus come from (I sincerely dislike using/relying on such things
when they seem to just "fall from the sky").

And if I may suggest this minor change for a future update to the
software: Please amend the documentation in the local installation of
Hephaestus with the paragraph detailing the core-hole lifetimes.

Best regards

Daniel

> On 11/13/2017 11:15 AM, Daniel Przyrembel wrote:
>> Still I can't see any reference to 'Keski-Rahkonen and Krause' in
>
>
> http://bruceravel.github.io/demeter/documents/Athena/hephaestus.html#absorption
>
>
> Here is the relevant bit from Feff:
>
> https://github.com/xraypy/feff85exafs/blob/master/src/COMMON/setgam.f
>
> Note that that bit in Feff is less sophisticated than you might think.
> My memory (Matt or John might remember better) is that Steve Zabinski
> (main author of Feff6) "interpolated" those values from the plots in the
> K&R paper.  This was done with a ruler back in the days before we had
> software tools for such chores.  I am not saying that the values in
> setgam.f are wrong -- just not as precise as you might imagine.
>
> B
>
>
>
> --
>   Bruce Ravel  ------------------------------------ bravel at bnl.gov
>
>   National Institute of Standards and Technology
>   Synchrotron Science Group at NSLS-II
>   Building 743, Room 114
>   Upton NY, 11973
>
>   Homepage:    http://bruceravel.github.io/home/
>   Beamline:    https://www.bnl.gov/ps/beamlines/beamline.php?r=6-BM
>   Software:    https://github.com/bruceravel
>   Demeter:     http://bruceravel.github.io/demeter/
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