[Ifeffit] [HOWTO] converting experimental mu(E) in cm^-1

[mauro at rulp.org]

On Thu, May 13, 2004 at 12:49:44PM -0500, Matt Newville wrote:
>
> I don't know if this exists right now, but it wouldn't be hard and
> would seem to help all self-absorption corrections. Currently,
> Ifeffit's bkg_cl()  does the opposite of this: scaling CL
> calculations to match experimental data for background subtraction
> and normalization.  It would not be hard to have this report the
> factors used so that the XAFS could be scaled back to the CL f".  
> The CL values for f" are tabularized in units of electrons (as
> natural for scattering) but that can be scaled to barns/atom.  It
> might be better to use the McMaster or Elam tables.
> 
> This would not be too difficult to do with Bruce's perl modules or
> in Ifeffit itself.  I'll put this on the Ifeffit to do list, but you
> might be able to roll something quick-n-dirty like this yourself
> faster than I get it in, especially since you're only working with

Ifeffit's bkg_cl() seems a good starting point I will look forward for it
and try to do something... (as soon as possible)

> one system....  I think all you'd have to do is scale the normalized
> XAFS to the edge jump from the tables.

I have noticed that sometimes it isn't enough to scale the edge jump but
also to subtract a linear function at the post-edge to adapt the slope to
the tabulated.

> 
> Are you working at the x-ray reflectivity critical angle (probably a 
> property solely of the SiO2 layer, though 15A is thin!), or at a 
> multilayer Bragg peak?

The standing wave field is shifted changing the angle of incidence in the
vicinity of the first-order multilayer Bragg peak, to vary the contribution
of different regions. Then XAFS measurement is done for the chosen standing
wave filed position.

>  
> Anyway, this seems wonderfully complicated -- congratulations!!
>  

Thank you very much,
Mauro

--
  Mauro Rovezzi <mauro at rulp.org> - Physics student
  University of Rome "Tor Vergata", ESRF Beamline BM8 - GILDA