Electron-impact ionization of Si IV-VIII relevant for inertial confinement fusion

TL;DR

This paper presents detailed calculations of electron-impact ionization cross sections and rates for silicon ions relevant to inertial confinement fusion, using advanced atomic physics methods and semi-empirical modeling, validated against measurements.

Contribution

It introduces a comprehensive approach combining multiple theoretical methods and semi-empirical formulas to accurately determine ionization rates for silicon ions in hot plasmas.

Findings

Agreement with measurements improves with higher ion charge.

Configuration interaction significantly affects low-energy cross sections.

The model is reliable up to temperatures of 10^8 K.

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. Configuration interaction is taken into account and is shown to affect the cross section at low energy, in particular for Si$^{3+}$. The rate coefficient is then expressed in terms of these parameters and is represented in a large temperature interval, up to 10$^8$ K. As expected, the agreement with measurements improves for increasing ion charges, confirming the applicability of our approach to hot plasma studies such as inertial-confinement fusion, and its reliability.