[Ifeffit] Self absorption Correction

Tue Feb 3 03:45:28 CST 2009

Hi,

In the "J. Phys. III (France)" paper you have the expression to 
calculate the "information depth"-magnitude.
Self absorption will take place if this magnitude is smaller than 
your fine powder size.

Typically, for a non-diluted material "information depth"-magnitude 
is (in microns) equal to one tenth of the measured edge energy (in 
keV)  that should be compared to your powder grain size.

Carlos Prieto

At 08:51 03/02/2009, you wrote:
>Hi,
>Thanks Richard and Carlos for the the links.
>But is the "Fluo"-Algorithm for self absorption correction also valid if
>I have the concentrated sample (standard) applied as a fine powder to a
>carbon tape or is it only valid for much much thicker samples?
>
>thanks,
>Jens
> > ------------------------------
> >
> > Message: 4
> > Date: Mon, 2 Feb 2009 09:51:10 -0500
> > From: Richard Mayes <rtmayes at gmail.com>
> > Subject: Re: [Ifeffit] Self absorption Correction
> > To: XAFS Analysis using Ifeffit <ifeffit at millenia.cars.aps.anl.gov>
> > Message-ID:
> >       <5a2a54820902020651nfaf1af7q4ec435fc207fc38a at mail.gmail.com>
> > Content-Type: text/plain; charset="iso-8859-1"
> >
> > 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 at 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
> >>
> >> _______________________________________________
> >> Ifeffit mailing list
> >> Ifeffit at millenia.cars.aps.anl.gov
> >> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
> >>
> >>
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>
> >
> > ------------------------------
> >
> > Message: 5
> > Date: Mon, 02 Feb 2009 16:59:19 +0100
> > From: Carlos Prieto <cprieto at icmm.csic.es>
> > Subject: Re: [Ifeffit] Self absorption Correction
> > To: XAFS Analysis using Ifeffit <ifeffit at millenia.cars.aps.anl.gov>
> > Message-ID: <20090202155915.DFCAE9AD3E at estafeta.csic.es>
> > Content-Type: text/plain; charset="iso-8859-1"; format=flowed
> >
> > Jens,
> >
> > Let me give you an old reference (but still
> > usefull) for the self absorption treatment:
> >
> > R. Casta?er 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/OverAbsorption>http://www.xafs.org/Experiment/OverAbsorption 
>
> >> (this is a link from the tutorials page of 
> <http://www.xafs.org>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>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
> >> <<mailto:jens.kruse at uni-rostock.de>jens.kruse at 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
> >>
> >> _______________________________________________
> >> Ifeffit mailing list
> >> 
> <mailto:Ifeffit at millenia.cars.aps.anl.gov>Ifeffit at millenia.cars.aps.anl.gov
> >> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
> >>
> >>
> >> _______________________________________________
> >> Ifeffit mailing list
> >> Ifeffit at millenia.cars.aps.anl.gov
> >> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
> >>
> >
> >
> > ================================
> > Carlos Prieto
> > Instituto de Ciencia de Materiales de Madrid CSIC
> > Cantoblanco, 28049 - MADRID (Spain)
> > Tel.: 91 3349017
> > e-mail: cprieto at icmm.csic.es
> > =================================
> >
> >
> >
> >
> > ------------------------------
> >
> > _______________________________________________
> > Ifeffit mailing list
> > Ifeffit at millenia.cars.aps.anl.gov
> > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
> >
> >
> > End of Ifeffit Digest, Vol 72, Issue 2
> > **************************************
> >
> >
>
>--
>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
>
>_______________________________________________
>Ifeffit mailing list
>Ifeffit at millenia.cars.aps.anl.gov
>http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

================================
Carlos Prieto
Instituto de Ciencia de Materiales de Madrid CSIC
Cantoblanco, 28049 - MADRID (Spain)
Tel.: 91 3349017
e-mail: cprieto at icmm.csic.es
================================= 