[Ifeffit] Self-absorption xmu units

Matteo Busi basebush at gmail.com
Mon Apr 4 05:09:52 CDT 2016

Hi Matt.

Thanks for the hints, they are very useful.

What would you suggest to use if not the bkg?
Regarding the xmu(E) I have been using exactly the values exported through
the .xmu ascii file.
I have been reading though the Athena's user guide and I didn't find any
hint about which unit I could assign to them.
Anyway I would like to get them with the cm^-1 units which would suit with
the correction expression I want to perform. How can this be done?
My idea was to divide the xmu data by the penetration depth in the sample
(i.e. the radius of the capillar sample). Is this correct? Can this be
applied to the bkg data aswell?

Moreover the data I have is not scanned through the Cu fluorescence energy
you have mentioned (8046 eV). Would you recommend to use data from Chantler
or Cromer-Liberman? And how can I merge it with my other measured data to
make it unit meaningful?

Thanks and regards,

I report our previous conversation for reference:

> What I am trying to do is to perform a new developed self-absorption
> correction using collected fluorescence absorption coefficient data on a
> CuSO4 (pentahydrate) capillar (cylinder) and spherical sample with Cu as
> absorber, having different values of molarity and penetration depth.
> The correction expression requires these measured quantity:
> ?X(E) : the absorption coefficient due to a given core excitation of the
> absorbing atom
>               - I used the background function for this ( bkg(E))

Wouldn't using bkg(E) suppress the fine-structure you are trying to
recover?  Anyway what are the units, are you normalizing bkg(E) to
something meaningful?  I would suggest using data from Chantler or
Cromer-Liberman here.   Or perhaps match mu(E) or bkg(E) to these.

> ?o = ?(E) : photoelectric total linear absorption coefficient of the
> sample at incident energy E
>                    - I used the xmu(E) for this

Again, be mindful of what the units are.

> ?h = ?(E) :photoelectric total linear absorption coefficient of the sample
> at fluorescence emission Ef
>                    - I used the xmu(Ef) with Ef the K absorption edge of
> Cu ( 8.9789 eV)

I am pretty sure that this is not what you want.  You probably want mu(E)
at the Cu fluorescence energy (8.046  keV). This can make a significant
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