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 <rtma...@gmail.com> > > Subject: Re: [Ifeffit] Self absorption Correction > > To: XAFS Analysis using Ifeffit <ifeffit@millenia.cars.aps.anl.gov> > > Message-ID: > > <5a2a54820902020651nfaf1af7q4ec435fc207fc...@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.kr...@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@millenia.cars.aps.anl.gov > >> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit > >> > >> > > -------------- next part -------------- > > An HTML attachment was scrubbed... > > URL: > http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20090202/22fbb148/attachment-0001.html > > > > > > ------------------------------ > > > > Message: 5 > > Date: Mon, 02 Feb 2009 16:59:19 +0100 > > From: Carlos Prieto <cpri...@icmm.csic.es> > > Subject: Re: [Ifeffit] Self absorption Correction > > To: XAFS Analysis using Ifeffit <ifeffit@millenia.cars.aps.anl.gov> > > Message-ID: <20090202155915.dfcae9a...@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.kr...@uni-rostock.de>jens.kr...@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@millenia.cars.aps.anl.gov>Ifeffit@millenia.cars.aps.anl.gov > >> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit > >> > >> > >> _______________________________________________ > >> Ifeffit mailing list > >> Ifeffit@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: cpri...@icmm.csic.es > > ================================= > > > > > > > > > > ------------------------------ > > > > _______________________________________________ > > Ifeffit mailing list > > Ifeffit@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@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: cpri...@icmm.csic.es ================================= _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit