Abstract
Several total and partial photoionization cross section calculations, based on both theoretical and empirical approaches, are quantitatively evaluated with statistical analyses using a large collection of experimental data retrieved from the literature to identify the state of the art for modeling the photoelectric effect in Monte Carlo particle transport. Some of the examined cross section models are available in general purpose Monte Carlo systems, while others have been implemented and subjected to validation tests for the first time to estimate whether they could improve the accuracy of particle transport codes. The validation process identifies Scofield's 1973 non-relativistic calculations, tabulated in the Evaluated Photon Data Library(EPDL), as the one best reproducing experimental measurements of total cross sections. Specialized total cross section models, some of which derive from more recent calculations, do not provide significant improvements. Scofield's non-relativistic calculations are not surpassed regarding the compatibility with experiment of K and L shell photoionization cross sections either, although in a few test cases Ebel's parameterization produces more accurate results close to absorption edges. Modifications to Biggs and Lighthill's parameterization implemented in Geant4 significantly reduce the accuracy of total cross sections at low energies with respect to its original formulation. The scarcity of suitable experimental data hinders a similar extensive analysis for the simulation of the photoelectron angular distribution, which is limited to a qualitative appraisal.
Highlights
P HOTOIONIZATION is important in various experimental domains, such as material analysis applications, astrophysics, photon science and bio-medical physics
The validation analysis encompasses various areas of investigation: the evaluation of possible systematic effects related to the characteristics of reference data, the evaluation of cross section models covering a wide energy range, the evaluation of specialized models with limited energy coverage and the appraisal of the capability of the examined cross section calculations to describe the photoelectric effect at the low energy end
Some of the total cross section models considered in this study cover a wide energy range: those based on Scofield’s 1973 non-relativistic calculations, Storm and Israel’s compilation and Biggs-Lighthill’s parameterization, both in its original form and in the modified version used by Geant4
Summary
P HOTOIONIZATION is important in various experimental domains, such as material analysis applications, astrophysics, photon science and bio-medical physics. This paper is concerned with modeling the physics of photoionization in a pragmatic way: the simulation of this process in general purpose Monte Carlo codes for particle transport. The analysis documented here evaluates the methods adopted in widely known Monte Carlo systems for the calculation of photoelectric cross sections for the elements of the periodic table, as well as other modeling approaches not yet implemented in these codes. This investigation aims to assess the capabilities of Monte Carlo codes for particle transport in this respect, and identify the state of the art for the simulation of the photoelectric effect. The simulation of the atomic relaxation following the ionization of an atom has been treated in previous publications [19]––[22], it is not addressed in this paper
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
