Re: [Ifeffit] Self-Absorption Corrections
hi all, Here is a gif of Nb2O5 at Nb K-edge and TiO2 at Ti K-edge. Both collected withb same geometry and detectors and same BL (SSRL 11-2). Fluo was collected at 90° to the beam (while transmission data was collected on the exact same sample). both spectra are normalized. Is there not any remaining self-absorption in the fluo spectrum for Nb2O5, despite data collected at 90° ?? (while TiO2 sounds fine, as Troeger predicted ?). thank for your expertise ! -- Francois FARGES Laboratoire des Géomatériaux Université de Marne la Vallée 5 Bd Descartes-Champs S/Marne 77454 Marne la Vallée cedex 2 TEL: 01 49 32 90 57 from outside France: +33 1 49 32 90 57 FAX: 01 49 32 91 37 from outside France: +33 1 49 32 91 37
On Tuesday 29 July 2003 04:07 am, Francois Farges wrote:
both spectra are normalized. Is there not any remaining self-absorption in the fluo spectrum for Nb2O5, despite data collected at 90° ?? (while TiO2 sounds fine, as Troeger predicted ?).
It's hard to know how to interpret your data unless you tell us how thick the samples are. B -- Bruce Ravel ----------------------------------- ravel@phys.washington.edu Code 6134, Building 3, Room 222 Naval Research Laboratory phone: (1) 202 767 5947 Washington DC 20375, USA fax: (1) 202 767 1697 NRL Synchrotron Radiation Consortium (NRL-SRC) Beamlines X11a, X11b, X23b, X24c, U4b National Synchrotron Light Source Brookhaven National Laboratory, Upton, NY 11973 My homepage: http://feff.phys.washington.edu/~ravel EXAFS software: http://feff.phys.washington.edu/~ravel/software/exafs/
On Tuesday 29 July 2003 04:07 am, Francois Farges wrote:
both spectra are normalized. Is there not any remaining self-absorption in the fluo spectrum for Nb2O5, despite data collected at 90° ?? (while TiO2 sounds fine, as Troeger predicted ?).
It's hard to know how to interpret your data unless you tell us how thick the samples are.
3 mu filters as made by the exafs company so it don't know their thickness exactly. the angles were the same so that's not the problem. I ve much more data that shows exactly the same. FF -- Francois FARGES Laboratoire des Géomatériaux Université de Marne la Vallée 5 Bd Descartes-Champs S/Marne 77454 Marne la Vallée cedex 2 TEL: 01 49 32 90 57 from outside France: +33 1 49 32 90 57 FAX: 01 49 32 91 37 from outside France: +33 1 49 32 91 37
Francois,
Here is a gif of Nb2O5 at Nb K-edge and TiO2 at Ti K-edge. Both collected withb same geometry and detectors and same BL (SSRL 11-2). Fluo was collected at 90° to the beam (while transmission data was collected on the exact same sample).
both spectra are normalized. Is there not any remaining self-absorption in the fluo spectrum for Nb2O5, despite data collected at 90° ?? (while TiO2 sounds fine, as Troeger predicted ?).
Clearly - like you say -, for Nb2O5, the amplitude of the fluorescence scan is reduced compared to the transmission data. Nevertheless I'm more surprised that the TiO2 scans match even near the absorption edge. Although I find it hard to discuss your experiments without knowing the details here are two ideas that came to my mind: * You can't get an exit angle of exactly 90 deg, it's always a bit smaller. Therefore selfabsorption won't vanish completely * The amplitude damping, even at identical geometries, depends on which fraction of the overall absorption coefficient comes from the absorber. (The damping is something like mu_absorber(E)/(mu_tot(E)+g*mu_tot(E_fl)) .) I would expect this fraction to be larger and the selfabsorption to be worse for Ni.
and anyway one needs a code with all the angles allowed to vary.
As far as I understand the mathematics in Corwin's paper, phi and theta can be varied independently. The phi+theta=90 condition seems to be only a limitation of the "sabcor" program that only asks for phi in its input file. Peter -- -------------------------------------------------------------- Peter Pfalzer Universitaet Augsburg Tel: +49-821-598-3215 Lehrstuhl fuer Experimentalphysik II Fax: +49-821-598-3411 Universitaetsstr. 1 D-86135 Augsburg Germany Peter.Pfalzer@physik.uni-augsburg.de --------------------------------------------------------------
participants (3)
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Bruce Ravel -
Francois Farges -
Peter Pfalzer