[Ifeffit] polarization in Artemis

Bruce Ravel bravel at bnl.gov
Sun May 24 13:50:39 CDT 2015


Everything in the discussion between Eugenio and Matt is stuff I agree 
with, except ...

When I rewrote Artemis, one of the motivations was that I wanted to 
write my own pathfinder rather than to continue using the one in Feff. 
My main motivation was fuzzy degeneracy 
(http://bruceravel.github.io/demeter/artug/extended/fuzzy.html) plus I 
wanted to correct a few other things I saw as shortcomings.

When I was writing it years ago, I didn't immediately see an easy way to 
consider polarization correctly while also doing fuzzy degeneracy 
correctly.  I have since figured that out, but years went by and only 
one person ever asked me about polarized feff calculations in Artemis. 
So I never implemented it.

It's a funny thing, when you wait for a bus, none comes, then two show 
up at once.  A month ago, I was asked about polarization in Artemis, and 
now Eugenio brings it up!

Polarization works (although it needs testing) in the very latest code 
in github.  But I did that work since the last time I built a Windows 
installer.  Ellipticity does not yet work (in Artemis -- it works just 
fine in Feff, but Artemis does not deliver the ellipticity-dependent 
calculation to the user).

Anyway, I will try to find a few hours this week to build a new Windows 
installer, which will included the ability to consider linear polarization.

 > Artemis used to make this very easy (sum paths without fitting),  but
 > I don't recall how to do this in the latest version.

Still is easy.  Well, I think it is.  YMMV :)



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

  National Institute of Standards and Technology
  Synchrotron Science Group at NSLS-II
  Building 535A
  Upton NY, 11973

  Homepage:    http://bruceravel.github.io/home/
  Software:    https://github.com/bruceravel
  Demeter:     http://bruceravel.github.io/demeter/

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