[Ifeffit] questions concerning paper

s440697 at stud.uni-goettingen.de s440697 at stud.uni-goettingen.de
Thu May 22 06:32:37 CDT 2008


i have some questions concerning the xafs-formula in this paper (attached):
"Theoretical approaches to x-ray absorption fine structure" (July 2000).
The author explained on page 625 and 626 the parameters of this formula.
I think, most of you have read this paper.

I don't understand the meaning of lambda(k), the author wrote "... and
lambda(k) is the energy-dependent XAFS mean free path (not to be confused
with the de Broglie wavelength)."
My question is, the mean free path whereof? The propagating
photoelektron(wave) or the (back)scattered waves?

In the next sentence, what is the overall amplitude factor S_0^2? How is
it defined?

In conjunction with question one i don't understand the expression in the
next paragraph for the term e^{-2R/lambda}. The author wrote: "The decay
of the wave (which wave does he mean?) due to the mean free path or finite
lifetime (what does he mean?, finite lifetime of the emitted and
propagating photoelektron wave?) [including core-hole lifetime] of the
photoelectron is captured by ..." Is it right, that the emitted
photoelektron is detectable outside the sample?

Another parameter is the phase factor phi = arg f(k) "...reflects the
quantum-mechanical wavelike nature of the backscattering." Please explain
me the meaning of this parameter.

At the bottom of this page the author wrote: "...the Debye-Waller factor,
which is given to a good approximation by e^{-2 sigma^2 k^2}." In this
context he refers to figure 8, where k^2 chi(k) vs. k is plotted. I don't
understand this context because there is no chi in the approximation for
the Debye-Waller factor. Where comes the chi here?

I would be very grateful for any help you would offer to me.
Thank you very much for your help and time.

sincerely yours,

Eckhard Bosman
e.bosman at stud.uni-goettingen.de
+49 (0)551-39-14441
Raum: E0.104
Institut für Röntgenphysik
Friedrich-Hund-Platz 1
37077 Göttingen
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