Calculation of Photoelectric Absorption Coefficients
Photoelectric absorption is the primary interaction of low-energy X-rays with
matter. The atomic photoelectric cross section,
, is obtained from the atomic
scattering function f2 by
= 2 r0
f2 ,
where
r0 is the classical electron radius, and
is the wavelength.
The wavelength (in Angstrom) is related to the energy (in keV) of the
X-radiation by
1 
= 12.397 / keV .
f2 is one of the two semi-empirical atomic scattering
factors used for the description of interactions of low-energy X-rays with
matter.
Graphs of scattering functions are presented on the
X-Ray WWW Server of the Physics Department
of the University of Uppsala.
The program PHOTCOEF, written
for microprocessors running unter DOS and WINDOWS, calculates the cross
sections as well as the linear and mass coefficients for the photoelectric
absorption process and for all other photon interactions with elements,
chemical compounds, and for mixtures of elements and compounds. PHOTCOEF
calculates cross sections and coefficients by using tabulated standard data,
and by performing log-log interpolation for intermediate energy values.
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