Jens,

Since no one has answered yet, I'll chime in.  First let me direct you to a discussion of self-absorption and other sample-related distortions:  http://www.xafs.org/Experiment/OverAbsorption  (this is a link from the tutorials page of www.xafs.org).

As for your questions: 

I think that you should use the non-normalized XANES data to perform the SA correction. 

for the angle-in and angle-out meanings, see Grant Bunker's paper on self-absorption here:  http://gbxafs.iit.edu/training/Self_Absorption_effects.pdf

Now, how do you determine if you have self-absorption effects?  I have to defer here to those with more experience.  What you suggest sounds appropriate, but I'm not sure how you could determine this without studying multiple concentrations of your absorber and watch the signals, i.e. does a 10% increase in absorber concentration translate to a 10% increase in fluorescence yield (similar to what Matthew Marcus and Alain Manceau describe in their paper, from the over-absorption link above).

HTH,
-Rich

On Fri, Jan 30, 2009 at 11:49 AM, Jens Kruse <jens.kruse@uni-rostock.de> wrote:
Hi there,

I have measured a pure reference compound with high absorber
concentration in fluorescence mode (P K-edge XANES).  I tried to use the
Self absorption correction  included in Athena but I don't really
understand the results.
Fist: Do I have to use the edge step normalized spectrum or the spectrum
without normalization ? I tried both and the results  of course a quite
different. I would rather use the not normalized spectrum.
Second: the value "Angel in"  is this the angle between the incident
beam and the sample surface" and "Angle out"  the angle between the
sample surface and the detector position?
Third: More general- How can I identify a spectrum suffering self
absorption? Just comparing the relative peak intensities of total
electron yield signal with the fluorescence yield signal ?

thanks a lot for your comments,
cheers,
 Jens

--
Jens Kruse
Institute for Land Use
Faculty for Agricultural and Environmental Sciences
Rostock University
Justus-von-Liebig-Weg 6
18059 Rostock GERMANY
Phone: +49(0)381-498 3190

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