Jens, Let me give you an old reference (but still usefull) for the self absorption treatment: R. Castañer and C. Prieto, "Fluorescence detection of EXAFS in thin film samples", J. de Phys. III (France), 7, 337-349 (1997). Best regards Carlos Prieto At 15:51 02/02/2009, you wrote:
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/OverAbsorptionhttp://www.xafs.org/Experiment/OverAbsorption (this is a link from the tutorials page of http://www.xafs.orgwww.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.pdfhttp://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 <mailto:jens.kruse@uni-rostock.dejens.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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================================ Carlos Prieto Instituto de Ciencia de Materiales de Madrid CSIC Cantoblanco, 28049 - MADRID (Spain) Tel.: 91 3349017 e-mail: cprieto@icmm.csic.es =================================