[Ifeffit] Estimation of S02

[Leandro Araujo]

Hi Hiroshi,

your variation in SO2 does sound a bit too big, so I'll try to help
adding my 50c and hopefully more people will jump in.
It seems to me that your window in k-space is going a bit lower than
it should - you seem to be including signal from the xanes region in
your fit and that is not a good thing.
I did some really quick fits using your project and just changing the
window from k ~ 2-14 to k ~ 4.8-14. Then I got the following values:
  kw             amp
   1   1.0065350+/-0.0788250
   2   1.0359800+/-0.0888140
   3   1.0749950+/-0.0946640
 1-3  1.0322490+/-0.0866650
That seems a more reasonable variation to me. But maybe I'm being
tricked by the fact that you have a split first shell and the MSRDs
are not supposed to be very similar...
I would also suggest opening the r-window to the right side a little
bit. (By the way, that "bump" in the FT at ~ 1 Angstrom seems
unexpected for a Zr foil. Maybe check the background removal in
Athena?)

The above comments obviously do not address the fundamental questions
"why does SO2 change with k-weighting?" and "what's the best way to
determine SO2?". This was intentional, since much better qualified
people have previously written about it.
My guess is that you will find something if you search previous
threads in this mailing list. I would also suggest you check these
sites:
http://xafs.org/Tutorials
http://cars9.uchicago.edu/iffwiki/FAQ/FeffitModeling

Hope this helps,
Leandro


2008/10/7 Hiroshi Oji <oji-h at spring8.or.jp>:
> Dear all,
>
> Could you give me some advice on estimating the intrinsic loss factor (S02)?
>
> I am trying to estimate the S02 value in the curve-fitting analysis for
> Zr K-edge EXAFS.
>
> To do this, I did the curve-fitting analysis on the first shell of
> Fourier transform of Zr-K EXAFS of Zr-foil by Artemis. However, there
> was a marked difference between the amps obtained by the fitting,
> depending on the "Fit k-weights" as follows.
>
>        kw      amp
>        1       0.8145660 +/- 0.0486470
>        2       0.9230700 +/- 0.0673820
>        3       1.0439100 +/- 0.0854950
>        1,2,3   0.9081570 +/- 0.0722180
>
> Is this a usual thing?  I can't find the reasonable explanation why S02
> depends on "Fit k-weights".
>
> I attached the Artemis project file.
>
> Thank you in advance for your cooperation.
>
> Hiroshi Oji
>
> =========================================================
> 　Hiroshi Oji, Dr.
>  Industrial Application Division
>  Japan Synchrotron Radiation Research Institute (JASRI)
>  1-1-1 Kouto, Sayo-cho
>  Sayo-gun, Hyogo 679-5198
>  JAPAN
>  E-mail oji-h at spring8.co.jp
> =========================================================
>
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