Sample-related distortions to measured data
===========================================

This page contains information about various problems the XAS
experimentalist might encounter which are related to the physical
nature of the sample. The problems include *overabsorption* (sometimes
called, possibly wrongly, *self absorption*), sample *thickness*
effects, and sample *inhomogeneity* (or *pin hole*) effects.

Tutorials and software
----------------------

- A `treatment of overabsorption, thickness, and hole effects
  <https://docs.xrayabsorption.org/Experiment/OverAbsorption/overabsorption.pdf>`__
  in XAS data collection by Matthew Marcus and Alain Manceau. Source
  document: A. Manceau, M.A. Marcus, N. Tamura (2002) *Reviews in
  Mineralogy and Geochemistry*, **49**, 341-428.
  `DOI:10.2138/gsrmg.49.1.341 <https://doi.org/10.2138/gsrmg.49.1.341>`_

- Daniel Haskel's
  `page about his Fluo program <https://www3.aps.anl.gov/haskel/fluo.html>`__,
  which corrects XANES data for self-absorption in certain situations.
  `The Fluo document <https://docs.xrayabsorption.org/Experiment/OverAbsorption/fluo.pdf>`__ contains a mathematical
  derivation of a simple self-absorption correction.

- The `Athena <https://bruceravel.github.io/demeter>`__ program
  offers several algorithms which attempt to correct for
  self-absorption. Here is the relevant
  `document page <https://bruceravel.github.io/demeter/documents/Athena/process/sa.html>`__.

- `A discussion on self-absorption <https://millenia.cars.aps.anl.gov/pipermail/ifeffit/2007-November/003365.html>`__
  from
  `the Ifeffit mailing list <http://cars9.uchicago.edu/mailman/listinfo/ifeffit>`__.

Literature references
---------------------

#. E. A. Stern and K. Kim, *Thickness effect on the
   extended-x-ray-absorption fine-structure amplitude*, Phys. Rev. B
   (1981) **23**:8 pp 3781-3787 `DOI:10.1103/PhysRevB.23.3781
   <https://doi.org/10.1103/PhysRevB.23.3781>`_

#. K-q. Lu and E. A. Stern, *Size effect of powdered sample on EXAFS
   amplitude*, Nucl. Instrum. and Methods (1983) **212**, pp. 475-478
   `DOI:10.1016/0167-5087(83)90730-5 <https://doi.org/10.1016/0167-5087(83)90730-5>`_

#. D. L. Brewe, D. M. Pease, J. I. Budnick, *Corrections of residual
   fluorescence distortions for a glancing-emergence-angle x-ray-absorption
   technique* Phys. Rev. B **50**, 9025-9030 (1994).
   `DOI:10.1103/PhysRevB.50.9025 <https://doi.org/10.1103/PhysRevB.50.9025>`_

#. A. Ryazhkin, Y. Babanov, M. Takafumi, *Thickness inhomogeneity and
   fluorescence effects in EXAFS spectroscopy for powder samples: solution
   of the inverse problem*. J. Synchrotron Rad. (2001), **8**, 291-293.
   `DOI:10.1107/S0909049500020926 <https://doi.org/10.1107/S0909049500020926>`_

#. A. I. Frenkel, D. M. Pease, J. I. Budnick, P. Shanthakumar, T. Huang,
   *Application of Glancing Emergent Angle Flourescence for Polarized XAFS
   Studies of Single Crystals* J. Synchrotron Rad. **14**, 272-275
   (2007) `DOI:10.1107/S0909049507014409 <https://doi.org/10.1107/S0909049507014409>`_

#. A. Manceau, M. A. Marcus, N. Tamura, in *Quantitative speciation of
   heavy metals in soils and sediments by synchrotron X-raytechniques", in
   Applications of Synchrotron Radiation in Low-Temperature Geochemistry
   and Environmental Science*, P. Fenter, N. C. Sturchio, Eds., Reviews in
   Mineralogy and Geochemistry, Mineralogical Society of America,
   Washington DC, **49,** 341-428 (2002)
   `DOI:10.2138/gsrmg.49.1.341 <https://doi.org/10.2138/gsrmg.49.1.341>`_

#. C. H. Booth, F. Bridges, *Improved Self-Absorption Correction for
   Fluorescence Measurements of Extended X-Ray Absorption Fine-Structure*,
   Physica Scripta, **T115**, 202-204 (2005).
   `DOI:10.1238/physica.topical.115a00202 <https://doi.org/10.1238/physica.topical.115a00202>`_