xray::absorption::mcmaster(3pm) [debian man page]
Xray::Absorption::McMaster(3pm) User Contributed Perl Documentation Xray::Absorption::McMaster(3pm) "cross_section" Example: $xsec = Xray::Absorption -> cross_section($elem, $energy, $mode); @xsec = Xray::Absorption -> cross_section($elem, @energy, $mode); The $mode argument is different here than for the other resources. The options are "xsec", "photo", "coherent" and "incoherent", telling this method to return the full cross-section or just the photoelectric, coherent, or incoherent portions. The values for all cross-sections are computed as log-log polynomials as described in the original paper by McMaster et al. NAME
Xray::Absorption::McMaster - Perl interface to the McMaster tables SYNOPSIS
use Xray::Absorption; Xray::Absorption -> load("mcmaster"); See the documentation for Xray::Absorption for details. DESCRIPTION
This module is inherited by the Xray::Absorption module and provides access to the data contained in the 1969 McMaster tables. The data in this module, commonly referred to as "The McMaster Tables", was originally published as Compilation of X-Ray Cross Sections W.H. McMster, N. Kerr Del Grande, J.H. Mallett, J.H. Hubbell National Bureau of Standards UCRL-50174 Section II Revision 1(1969) Available from National Technical Information Services L-3 United States Department of Commerce This can be a bit difficult to find. IIT's Galvin library has kindly made a scan of it available: http://www.gl.iit.edu/govdocs/resources/xray.html The data is contained in a database file called mcmaster.db which is generated at install time from a flat text database of the McMster data. The data originally comes from mucal.f, a Fortran subroutine originally written by Dr. Pathikrit Bandhyapodhyay. The required Chemistry::Elements module is available from CPAN in the miscellaneous modules section. EDGE AND LINE ENERGIES
The McMaster data resource only includes K and L 1-3 edges. For light elements, it provides only a single L edge energy -- that for the L1 edge. For heavier elements it provides a single M energy, the energy of the M1 edge. It only supplies four generic fluorescence line energies, Kalpha, Kbeta, Lalpha, and Lbeta. In each case the energy provided is the energy of the brightest line of that sort. BUGS AND THINGS TO DO
o Make sure this handles fluorescence lines which are in other resources, but not in this resource in a sensible manner. o What happens if you call "line_toggle" when this is loaded? How about when elam was loaded but then you switch to this one? AUTHOR
Bruce Ravel, bruce@phys.washington.edu http://feff.phys.washington.edu/~ravel/software/Absorption/ perl v5.12.4 2011-07-30 Xray::Absorption::McMaster(3pm)
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Xray::Absorption::Chantler(3pm) User Contributed Perl Documentation Xray::Absorption::Chantler(3pm) NAME
Xray::Absorption::Chantler - Perl interface to the Chantler tables SYNOPSIS
use Xray::Absorption; Xray::Absorption -> load("chantler"); See the documentation for Xray::Absorption for details. DESCRIPTION
This module is inherited by the Xray::Absorption module and provides access to the data contained in the Chantler tables of anomalous scattering factors and line and edge energies. The data in this module, referred to as "The Chantler Tables", was published as C. T. Chantler Theoretical Form Factor, Attenuation, and Scattering Tabulation for Z = 1 - 92 from E = 1 - 10 eV to E = 0.4 - 1.0 MeV J. Phys. Chem. Ref. Data 24, 71(1995) This can be found on the web at http://physics.nist.gov/PhysRefData/FFast/Text/cover.html The Chantler data is available on the web at http://physics.nist.gov/PhysRefData/FFast/html/form.html More information can be found on the personal web page of C.T. Chantler http://optics.ph.unimelb.edu.au/~chantler/home.html The data contained in a database file called chantler.db which is generated at install time from the flat text files of the Chantler data. The data is stored in a Storable archive using "network" ordering. This allows speedy disk and memory access along with network and platform portability. The required "File::Spec", "Chemistry::Elements", and "Storable" modules are available from CPAN. METHODS
The behaviour of the methods in this module is a bit different from other modules used by "Xray::Absorption". This section describes methods which behave differently for this data resource. "get_energy" Example: $energy = Xray::Absorption -> get_energy($elem, $edge); This behaves similarly to the "get_energy" method of the other resources. When using the Chantler data resource, $edge can be any of K, L1-L3, M1-M5, N1-N7, O1-O5, or P1-P3. Line energies are not supplied with the Chantler data set. The line energies from the McMaster tables are used. "cross_section" Example: $xsec = Xray::Absorption -> cross_section($elem, $energy, $mode); This behaves slightly differently from the similar method for the McMaster and Elam resources. The Chantler tables contain anomalous scattering factors and the sum of the coherent and incoherent scattering cross-sections. The photo-electric cross-section is calculated from the imaginary part of the anomalous scattering by the formula mu = 2 * r_e * lambda * conv * f_2 where, "r_e" is the classical electron radius, lamdba is the photon wavelength, and conv is a units conversion factor. r_e = 2.817938 x 10^-15 m lambda = 2 pi hbar c / energy hbar*c = 1973.27053324 eV*Angstrom conv = Avagadro / atomic weight = 6.022045e7 / weight in cgs The $mode argument is different here than for the other resources. The options are "xsec", "f1", "f2", "photo", and "scatter" telling this method to return the full cross-section cross-section, the real or imaginary anomalous scattering factor, just the photoelectric crosss-section, or just the coherent and incoherent scattering, respectively. The values for f1 and f2 are computed by linear interpolation of a semi-log scale, as described in the literature reference. Care is taken to avoid the discontinuities at the edges. EDGE AND LINE ENERGIES
The Chantler data resource provides a fairly complete set of edge energies. Any edge tabulated on the Gwyn William's Table of Electron Binding Energies for the Elements (that's the one published by NSLS and on the door of just about every hutch at NSLS) is in the Chantler data resource. The Chantler data comes with the same, limited set of fluorescence energies as McMaster. BUGS AND THINGS TO DO
o It would be nice to improve the inter-/extrapolation near absorption edges. As it stands, these tables produce really poor DAFS output. AUTHOR
Bruce Ravel, bruce@phys.washington.edu http://feff.phys.washington.edu/~ravel/software/Absorption perl v5.12.4 2011-07-30 Xray::Absorption::Chantler(3pm)