[Ifeffit] Normalization in Athena

Matt Newville newville at cars.uchicago.edu
Tue Oct 27 15:44:20 CDT 2009

Hi Lisa,

On Mon, Oct 26, 2009 at 9:12 PM, Gudrun Lisa Bovenkamp
<bovenkamp at physik.uni-bonn.de> wrote:
> I am sure that Athena was tested a lot, but as Jeremy pointed out, which I think now is the answer: If the
> background is substracted before the fitting of the post edge. That is actually how we are normalizing
> XANES data in our group and that is what I tried in Athena.
> It is actually working much better with 2. order norm and flattening.

If you're concerned about normalization, do not flatten the data!!!

>  This time I attached a the example Athena project file.

I did not look closely at all the data in your project file, but the
first group listed "Pb113 norm in Athena" has E0 = 13037.76.
Extracting the mu(E) data, and looking in the region around E0 + 200
eV, I see these energy values:

so that, in fact. there are no data between E0+199 = 13236.76 eV and
E0+200 = 13237.76 eV.

> But with this approach I rarely get the spectrum oscillating around one.

Actually, you're not supposed to get a spectrum that oscillates around one.

Again, you will get a better normalization if you use a line
(Normalization order=2) and a range of 100 to 250eV.   When I do this
with the "Pb113 norm Athena" and "Pb125 norm in Athena" data in your
project, I get a mu(E) that starts out ~1 and decays away with energy,
just as it should.

The "norm in Orign" groups you have in your project all have about the
same value for mu(E) at E=E0+200eV, but are not well normalized.


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