[Ifeffit] (no subject)

[Bruce Ravel]

On Tuesday 12 July 2005 07:15, Dr. K.R.S. Priolkar wrote:
> Hi
> I wouldlike to know if it is possible to refine Ce L1 edge EXAFS using
> Artemis wherein there is a contribution of Ce L2 EXAFS.
>
> If yes, how to go about it?

Kaustubh

Wow.  That's an interesting question.  I have to confess that I have never
given this a lot of thought, but it seems like something that should be
possible. 

Before suggesting two possible solutions, I want to mention that those two
edges are about 380 volts, or 10 inverse angstroms, apart.  The wiggles from
the L2 edge should be quite low frequency by the time the L1 edge shows up.
It is possible that the background removal algorithm at the L1 edge will
remove most (maybe even all) of the contribution from the L2 edge because the
L2 oscillations will be below the frequency of the first shell.  Of course,
the L1 edge is really tiny, so the L2 might still be a big effect.

My first suggestion is to fit the L2 edge as best you can using Artemis
(assuming, perhaps without merit, that the L3 signal does not get in the
way).  Let Artemis write out the fitted chi spectrum out to, say 15 inverse
angstroms.  Then subtract the portion of the fitted L2 chi spectrum from the
L1 data in the region where they overlap.

My second suggestion is to run Feff for the L2 edge from within Artemis and
apply an enormous e0 shift to the paths from the L2 calculation.  I have no
confidence that such a large e0 shift will really work the way you want,
though.

Anyone else have any clever ideas for solving this with existing technology?
Any suggestions for improvements to Artemis to facilitate this sort of thing? 

B


-- 
 Bruce Ravel  ----------------------------------- bravel at anl.gov  -or-
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