polarized Feff

[Matt Newville <newville@cars.uchicago.edu>]

Alex, John,

I know I've asked this same question many years ago, but I'm
still confused, so maybe  others are confused too:

  How do I get a polarization average from Feff?

I'd like to average the polarization of an L edge over the ab
plane in a crystal.  A simple cos^2 is not good enough for L
edge, and I really want a polarization average.  Circular
polarization seems to be one approach.

=Question 0:  Should circular polarization along z give a
              polarized average of the ab plane?

Assuming it will, the doc says
   ELLIPITICY 1. 0. 0. -2.

would have circular polarization.

=Question 1:  Why -2?

=Question 2:  Do I also need to set
   POLARIZATION 1. 0. 0.
   (or anywhere else in the ab plane?)

My recollection is that this is needed.  The doc is somewhat
ambiguous.  The weird thing is that when I use

   POLARIZATION 1. 0. 0.
   ELLIPITICIY  1. 0. 0. 1.

I seem to get only paths with a finite Z component, and none in
the ab-plane.

Commenting out the ELLIPICITY card gives paths entirely within
the ab-plane, though it is not an average in the ab-plane.

Commenting out the POLARIZATION card gives paths entirely within
the ab-plane, but it appears that this gives no polarization
dependence at all.


Is there any way to turn degeneracy checking off?

Thanks,

--Matt

PS: I'm using Feff824.  I'm assuming this is the latest, but
    have no idea if this is actually the case.