| Description | Perl tools for X-ray Absorption Spectroscopy |
Demeter::Data::SelfAbsorption - Self-absorption corrections for mu(E) data
This documentation refers to Demeter version 0.9.26.
This role of Demeter::Data contains methods for calculating self-absorption corrections for mu(E) data using various algorithms.
saCompute the correction using one of the following methods:
This corrects mu(E) data using an algorithm developed by Bruce along with Ed Stern and Dani Haskel. This was first implemented by Dani Haskel and then reimplemented into the original Athena. It is the only correction method here that is applied to mu(E) data.
This is a correction to chi(k) that applies only in the thick sample limit.
This improvement on the Troger algorithm was developed by Corwin Booth and Bud Bridges and can applied to a sample of any thickness, although the density of the sample must be supplied. In the thick sample limit, it is identical to the Troger correction.
This correction to chi(k) computes the effects of normalization, i0, and self absorption using Xray::FluorescenceEXAFS. It is a fairly crude approximation and is only valid in the thick sample limit. It also does not consider the effect of incident or exit angle.
$data -> po -> strt_plot;
$data -> plot('k');
my ($sadata, $text) = $data->sa($method, formula=>$formula, in=>$angle_in
out=>$angle_out, thickness=>$thickness);
$sadata -> plot('k');
print $text;The method returns a reference to a Data object containing the corrected data and a scalar containing the textual response from the selected correction method.
The formula must be provided and must be specified using the syntax of Chemistry::Formula. Defaults for in and out are 45 degrees an the default for thickness is to compute in the thick sample limit.
The named arguments can appear in any order, but the first item in the argument list must be the correction method.
info_depthReturn arrays of wavenumber and information depth where the information depth represents the depth from which signal is retrieved from the sample. Essentially, this plots the energy dependence of the absorption length over the k-range of the data.
my ($ref_k, $ref_info) = $data->info_depth(formula=>$formula,
in=>$angle_in
out=>$angle_out);The returned values are array references.
See Demeter::Config for a description of the configuration system.
The program documentation for Fluo can be found at Dani's web site and includes the mathematical derivation: http://www.aps.anl.gov/xfd/people/haskel/fluo.html.
C. H. Booth and F. Bridges, Physica Scripta, T115, (2005) p. 202. DOI:10.1238/Physica.Topical.115a00202 See also Corwin's web site: http://lise.lbl.gov/RSXAP/
L. Troger, et al., Phys. Rev., B46:6, (1992) p. 3283 DOI: 10.1103/PhysRevB.46.3283
Another interesting approach to correcting self-absorption is presented in P. Pfalzer et al., Phys. Rev., B60:13, (1999) p. 9335. DOI: 10.1103/PhysRevB.60.9335
This is not implemented in Demeter because the main result requires an integral over the solid angle subtended by the detector. This could be implemented, but the amount of solid angle subtended it is not something one typically writes in the lab notebook. If anyone is really interested in having this algorithm implemented, contact Bruce.
B. Ravel, J. Synchrotron Radiat., 8:2, (2001) p. 314. DOI: 10.1107/S090904950001493X
See also the documentation for Atoms at Bruce's website for more details about it's fluorescence correction calculations.
W.T. Elam, B.Ravel, and J.R. Sieber, Radiat. Phys. Chem., 63, (2002) p. 121-128, DOI: 10.1016/S0969-806X(01)00227-4
Please report problems to the Ifeffit Mailing List (http://cars9.uchicago.edu/mailman/listinfo/ifeffit/)
Patches are welcome.
Bruce Ravel, http://bruceravel.github.io/home
http://bruceravel.github.io/demeter/
With help from Dan Olive and Corwin Booth
Copyright (c) 2006-2018 Bruce Ravel (http://bruceravel.github.io/home). All rights reserved.
This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See perlgpl.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.