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

       •   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