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
