Understanding the L-shell ionization mechanism through osmium atoms bombarded by 4-6 MeV/u fluorine ions

TL;DR

This study investigates the L-shell ionization mechanism in osmium atoms bombarded by fluorine ions at 4-6 MeV/u, combining experimental data with advanced theoretical models to understand ionization processes in heavy atoms.

Contribution

It introduces a comprehensive approach that combines multiple ionization mechanisms and theoretical models to accurately describe heavy-ion induced inner-shell ionization in heavy atoms.

Findings

ECUSAR-CSM-EC model best fits the experimental data

Theoretical calculations are about half the measured values without parameter re-evaluation

Re-evaluating atomic parameters improves agreement between theory and experiment

Abstract

The L-subshell ionization mechanism is studied in an ultra-thin osmium target bombarded by 4-6 MeV/u fluorine ions. Multiple ionization effects in the collisions are considered through the change of fluorescence and Coster-Kronig yields while determining L-subshell ionization cross sections from L-line x-ray production cross sections. The L-subshell ionization, as well as L-shell x-ray production cross sections so obtained, are compared with various theoretical approximations. The Coulomb direct ionization contributions is studied by (i) the relativistic semi-classical approximations (RSCA), (ii) the shellwise local plasma approximation (SLPA), and (iii) the ECUSAR theory, along with the inclusion of the vacancy sharing among the subshells by the coupled-states model (CSM) and the electron capture (EC) by a standard formalism. We find that the ECUSAR-CSM-EC describes the measured excitation function curves the best. However, the theoretical calculations are still about a factor of two smaller than the measured values. Such differences are resolved by re-evaluating the fluorescence and the Coster-Kronig yields. This work demonstrates that, in the present energy range, the heavy-ion induced inner-shell ionization of heavy atoms can be understood by combining the basic mechanisms of the direct Coulomb ionization, the electron capture, the multiple ionization, and the vacancy sharing among subshells, together with optimized atomic parameters.