[Ifeffit] quotation of figures

[Bruce Ravel]

On Wednesday 16 July 2008 12:04:26 s440697 at stud.uni-goettingen.de wrote:
> Hi,
> i have a print out of a talk (about XANES, XAFS and multiple
> scattering...) and i want to cite some figures (attached). Can anybody
> tell me the author etc...? I searched everywhere on the web (on several
> sites of XAFS-Summer Schools...). Unfortunately i do not have the talk as
> pdf-file only the print out. Maybe the talk is from Matt Newville? Maybe
> anybody recalls on this talk/slides or recognizes them?

Eckhard,

I do not know the provenance of those figures, but I would recommend
using the 3rd one with caution.

The disorder term in the exafs equation, as it is conventionally
expressed, is exp(-2 * k^2 * sigma^2).  The author of these figures
clearly got confused between the disorder and mean free path terms.
At the very least, you should photoshop or the gimp to fix that.

I also dislike the phrase "Debye-Waller factor" for the exafs disorder
term.  In crystallography, the Debye-Waller factor refers to disorder
of atoms about their lattice positions.  In exafs, the disorder is
about the path length of the N-body configuration -- clearly not the
same thing.  I am, apparently, in the minority on this topic --
"Debye-Waller factor" is in wide use in the exafs literature.  But, as
everyone here knows, I often like to stand up on my soapbox and yell
into the crowd. ;-)

Another thing -- I don't quite understand the middle panel of the
second figure.  That is not the cartoon I would use to describe the
operator in Fermi's golden rule.

B


-- 
 Bruce Ravel  ------------------------------------ bravel at bnl.gov

 National Institute of Standards and Technology
 Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2
 Building 535A
 Upton NY, 11973

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