[Ifeffit] Difference spectra

[Bruce Ravel]

On 05/30/2016 01:25 PM, sb2c08 at gmail.com wrote:
> We recently collected laser pump-probe XAS data out to k=9. The
> process to get the excited state is to take the laser off minus the
> laser on data. I'm a little unsure in terms of trying to fit the
> difference EXAFS and is it possible via Athena? So far I model the
> EXAFS of the excited state and take away from the ground state model
> and compare visually. The only way I can think is to work out the %
> conversion and add that % of laser off back to the difference data in
> order to get the real EXAFS of the excited state, which can be fitted
> through Athena. But this is really difficult and probably
> inaccurate?


Of course it's not possible to fit and EXAFS spectrum in Athena. 
Artemis is the program for fitting the EXAFS.

I am unclear on what you have tried so far, so I am a little unsure what 
kind of answer you are looking for.  Artemis was not really written with 
your sort of experiment in mind.  That said, if your problem is fit some 
theory from Feff to a measured spectrum with some fitting model -- that 
is what Artemis is for.  As with any difficult problem, you need to 
understand your data and your model and you need to understand Artemis 
well enough to implement the fit.  But there is no magical, hidden 
button that says "fit my pump-probe data."

B

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

  National Institute of Standards and Technology
  Synchrotron Science Group at NSLS-II
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  Upton NY, 11973

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