ARE: [Ifeffit] Re: Ifeffit Digest, Vol 5, Issue 1

[Bruce Ravel]

On Friday 04 July 2003 02:48 am, SCHLEGEL Michel 177447 wrote:
> I think an evaluation of the spectrum noise may be obtained 
> from the FT contributions peaking at high 'distances' (e.g.,
> > 10Å). Hence, with a correct script, we should be able to:
> - extract chi(k) functions from individual XAS spectra
> - perform FTs for these spectra,
> - perform inverse FT on the spectra over a given limit, and 
>   calculate s from that,
> - usecalculated s values to sum weight-average individual 
>   XAS spectra.
> 
> As I'm a very lousy IFEFFIT user (means that I've stopped 
> short from hitting buttons on Athena and Artemis), I would 
> humbly ask Bruce if there's any chance to see such a methodology
> implemented on Athena one of these days (not in a hurry, though) 

The short answer is yes.  Currently Athena sets the noise to 1 for all
scans involved in the merge.  However, Ifeffit offers the very handy
chi_noise function, which computes the noise in a manner similar to
what Michel suggests.  (In fact, it computes the average of the
chi(R) spectrum between 15 and 25 Å.)  It would be simple matter to
weight each spectrum by that number and to give the user the option of
choosing how to do the weighting.

I'll put it on my list of things to do, which seems to grow faster
than I can shrink it!

Thanks,
B

-- 
 Bruce Ravel  ----------------------------------- ravel at phys.washington.edu
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