Contribution of high-nl shells to electron-impact ionization processes

TL;DR

This study investigates how high-nl shell excitations significantly influence electron-impact ionization cross sections, especially in highly charged tungsten ions, revealing that high shells and orbitals substantially increase ionization probabilities.

Contribution

It provides detailed relativistic calculations demonstrating the large impact of high-nl shell excitations on ionization cross sections, a novel insight for heavy ion collision studies.

Findings

High shells (n >= 9) double the indirect ionization cross sections.

Excitations to l=4 orbitals contribute most significantly.

Radiative damping reduces cross sections by about half.

Abstract

The contribution to electron-impact ionization cross sections from excitations to high-nl shells and a consequent autoionization is investigated. We perform relativistic subconfiguration-average and detailed level-to-level calculations for this process. Ionization cross sections for the W27+ ion are presented to illustrate the large influence of the high shells (n >= 9) and orbitals (l >= 4) in the excitation-autoionization process. The obtained results show that the excitations to the high shells (n >= 9) increase cross sections of the indirect ionization process by a factor of 2 compared to the excitations to the lower shells (n <= 8). The excitations to the shells with orbital quantum number l = 4 give the largest contribution comparedwith the other orbital quantum numbers l. Radiative damping reduces the cross sections of the indirect process approximately twofold in the case of the level-to-level calculations. Determined data show that the excitation-autoionization process contributes approximately 40% to the total ionization cross sections.