[Ifeffit] Right way of choosing E0 in Athena

[Vadim G Palshin]

>Since you know the spectra are well calibrated relative
>to one another, I would use a single E0 for all
>background subtractions.  In such a situation, I tend to
>play with the background parameters for one of the
>spectra and then apply these background
>parameters to all other spectra.
Thanks, Matt! Yes, that’s pretty much what I have been doing, just had some
trouble getting reasonable fit values for E0’s in my last set of samples.
Aligning chi(k) of the standard to theory – great guide, Shelly! – and then
applying  the same parameters to the other spectra helped solve this. Now,
more questions:
1. Many experts advise to do multiple k-weight fitting to deal with
correlated variables. Should one always use multiple k-weights, or is it
better to switch to one kw value once the correlations are taken care of –
to refine the remaining variables? Does it make any difference?
2. When modeling the Debye-Waller factors for multiple-scattering paths, is
it possible to express them in terms of the sigma^2’s of single-scattering
paths that correspond to the atoms involved in the multiple scattering
events; i.e. for a core—atomA—atomB—core path, can sigma^2 be obtained by
some combination of core—atomA and core—atomB sigmas? It seems intuitively
that they should be related, and also that the amplitudes of multiple
scattering paths should be more sensitive to disorder. Does this make any
sense?
Thanks again for your replies!
Vadim.