Provided by: libxray-absorption-perl_3.0.1-4_all 
NAME
Xray::Absorption::Elam - Perl interface to the Elam tables
SYNOPSIS
use Xray::Absorption;
Xray::Absorption -> load("elam");
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 1999 Elam tables of absorption cross-sections and line and edge energies.
The data in this module, here referred to as "The Elam Tables", will be published real
soon. The compilation of data is the work of Tim Elam (tim.elam@nrl.navy.mil).
The data is contained in a database file called elam.db which is generated at install time
from a flat text database of the Elam 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 "Chemistry::Elements", "Math::Spline", and "Math::Derivative" modules are
available from CPAN.
LITERATURE REFERENCES
K-shell fluorescence yield below Z=11 from new fits in J. H. Hubbell et. al., J. Chem.
Phys. Ref. Data, Vol. 23, No. 2, 1994, pp. 339-364.
Fluorescence yields and Coster-Kronig transition rates for K and L shells Krause, J. Phys.
Chem. Ref. Data, Vol. 8, No. 2, 1979, pp. 307-327. values for wK, wL2,and f23 are from
Table 1. (values for light atoms in condensed matter) (note that this produces a large
step in f23 values at z=30, see discussion in reference section 5.3 L2 Subshell and
section 7 last paragraph)
Values of wL1 for Z=85-110 and f12 for Z=72-96 from Krause were modified as suggested by
W. Jitschin, "Progress in Measurements of L-Subshell Fluorescence, Coster-Kronig, and
Auger Values", AIP Conference Proceedings 215, X-ray and Inner-Shell Processes,
Knocxville, TN, 1990. T. A. Carlson, M. O. Krause, and S. T. Manson, Eds. (American
Institute of Physics, 1990).
Fluorescence yields and Coster-Kronig transition rates for M shells Eugene J. McGuire,
"Atomic M-Shell Coster-Kronig, Auger, and Radiative Rates, and Fluorescence Yields for Ca-
Th", Physical Review A, Vol. 5, No. 3, March 1972, pp. 1043-1047.
Fluorescence yields and Coster-Kronig transition rates for N shells Eugene J. McGuire,
"Atomic N-shell Coster-Kronig, Auger, and Radiative Rates and Fluorescence Yields for 38
<= Z <= 103", Physical Review A 9, No. 5, May 1974, pp. 1840-1851. Values for Z=38 to 50
were adjusted according to instructions on page 1845, at the end of Section IV.a., and the
last sentence of the conclusions.
Relative emission rates, fits to low-order polynomials, low-Z extrapolations by hand and
eye data from Salem, Panossian, and Krause, Atomic Data and Nuclear Data Tables Vol. 14
No.2 August 1974, pp. 92-109. M shell data is from T. P. Schreiber and A. M. Wims, X-ray
Spectrometry Vol. 11, No. 2, 1982, pp. 42-45. Small, arbitrary intensities assigned to
Mgamma and Mzeta lines.
Cross sections are in cm2/gm vs energy in eV. Berger and Hubbell above 1 keV, Plechaty
et. al. below.
Reference: M. J. Berger and J. H. Hubbell, XCOM: Photon Cross Sections on a Personal
Computer, Publication NBSIR 87-3597, National Bureau of Standards, Gaithersburg, MD, 1987.
Machine-readable data from J. H. Hubbell, personal communication, Nov. 9, 1998. The data
were updated as of May 7, 1998 (XCOM Version 2.1).
Reference: Plechaty, E. F., Cullen, D. E., and Howerton,R.J, "Tables and Graphs of Photon
Interaction Cross Sections from 0.1 keV to 100 MeV Derived from the LLL Evaluated Nuclear
Data Library," Report UCRL-50400, Vol. 6, Rev. 3, NTIS DE82-004819, Lawrence Livermore
National Laboratory, Livermore, CA. (1981). Machine-readable data from D. B. Brown, Naval
Research Laboratory.
METHODS
The behaviour of the "get_energy" method 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 and methods offered by this module which are not
available for other resources.
"get_energy"
Example:
$energy = Xray::Absorption -> get_energy($elem, $edge)
This behaves similarly to the "get_energy" method of othe resources, except there are
some differences regarding the syntax of specifying $edge. When using the Elam data
resource, $edge can be any of K, L1-L3, M1-M5, N1-N7, O1-O7, or P1-P3. To get a
fluorescence line, you may use any Siegbahn or IUPAC symbol to specify the line. See
the pod in "Xray::Absorption" for details about these symbols. You may also specify a
"generic" Siegbahn symbol, such as Kalpha. The energy that is returned depends on the
value of an internal variable which may be set using the "line_toggle" method. If the
toggle is set to "brightest", the energy of the brightest line of the class is
returned. In the case of "Kalpha", the energy or the Kalpha1 line is returned. If
the toggle is set to "weighted" then the intestity weighted average energy of all
lines of the class is returned. "weighted" is the default.
"line_toggle"
Toggle the method of computing a generic fluorescence line between "weighted" and
"brightest". This determines the response to a use of "get_energy" like this:
$energy = Xray::Absorption -> line_toggle("brightest");
$energy = Xray::Absorption -> get_energy("cu", "kalpha");
$energy = Xray::Absorption -> line_toggle("wieghted");
$energy = Xray::Absorption -> get_energy("cu", "kalpha");
When "weighted" is selected, this returns the intensity weighted energy of the various
Kalpha lines. When "brightest" is chosen, this returns the energy of the Kalpha1 line
because that is the brightest Kalpha line. The default is "weighted". Case does not
matter for the argument, but spelling does. If the argument is not spelled correctly
then the calculation method is not toggled.
"fluor_yield"
Return the fluorescence yield for an atomic symbol and edge
$fyield = Xray::Absorption -> fluor_yield("cu", "k");
The value returned is the probability of an fluorescent x-ray being emitted for an
absorption event. Data comes from M. O. Krause, J. Phys. Chem. Ref. Data 8, 307
(1979) Returns -1 for non-interpretable input
"edge_jump"
Return edge jump ratio for an atomic symbol and edge
$jump = Xray::Absorption -> edge_jump("cu", "k");
The value returned is the ratio of the above-edge absorption coefficient to the below-
edge coefficient
"get_intesity"
Example:
$intensity = Xray::Absorption -> get_intesity($elem, $symbol)
Get the relative amount of the line specified by $symbol for the element $elem. $elem
can be a two letter symbol, a full name, or a Z number. $symbol may be either a
Siegbahn or IUPAC symbol. The intesities are such that all lines of a type (e.g. all
Kalpha lines) have intesities which sum to 1. If $elem or $symbol is not recognized,
then this returns 0.
"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 using spline interpolation as described
in the paper by Elam, Ravel, and Siebert.
EDGE AND LINE ENERGIES
The Elam data resource provides a fairly complete set of edge and line 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 Elam data resource. Additionally, a large but not exhaustive collection of line
energies is tabulated. Every line in the table in the SYMBOLS FOR FLUORESCENCE LINES
section of the "Absorption.pm" pod is included in the Elam tables. A reasonable value for
the relative line intensity if also included in this table. See (the elam reference) for
a discussion of which lines were included in the tables and how the intensities were
calculated.
BUGS AND THINGS TO DO
• The "weighted" option for "get_energy" is not quite right in that it counts in lines
from different edges. While that might be appropriate, there is some question as to
the relative weights of lines from different edges. So a better solution would be to
only use lines from the edge directly below the chosen energy.
AUTHOR
Bruce Ravel, bruce@phys.washington.edu
http://feff.phys.washington.edu/~ravel/software/Absorption/