Electron-impact ionization of Si IV–VIII in hot plasmas

Abstract

In this work, we investigate the ionization of silicon by electron impacts in hot plasmas. Our calculations of the cross sections and rates rely on the Coulomb-Born-Exchange, Binary-Encounter-Dipole and Distorted-Wave methods implemented in the Flexible Atomic Code (FAC), and are compared with measurements and other theoretical values. We use a semi-empirical formula for the cross section, which involves a small set of adjustable parameters. The rate coefficient is then expressed in terms of these parameters and is represented in a large temperature interval, up to 108 K. As expected, the agreement with measurements improves for increasing ion charges, confirming the applicability of our approach to hot plasma studies such as inertialconfinement fusion, and its reliability. Configuration interaction is taken into account and is shown to affect the cross section at low energy, in particular for Si3+.