Double-ionization mechanisms of magnesium driven by electron impact

TL;DR

This paper investigates the double ionization of magnesium caused by electron impact using classical mechanics, classifying mechanisms and comparing theoretical predictions with experimental data.

Contribution

It introduces a comprehensive classical four-body model that classifies double-ionization mechanisms and predicts their relative importance, aligning with experimental observations.

Findings

Eight double-ionization mechanisms identified

Delay and inner shell ionization mechanisms depend on electron correlations

Theoretical predictions agree with experimental prominence of mechanisms

Abstract

We study double ionization of Mg by electron impact through the vantage point of classical mechanics. We consider all electron-electron correlations in a Coulomb four-body problem, where three electrons belong to the atom and the fourth electron causes the impact ionization. From our model we compute the double-ionization probability of Mg for impact energies from 15, to 125 eV. Double ionization occurs through eight double-ionization mechanisms, which we classify into four categories: inner shell capture, direct, delay and ionized inner shell mechanisms. We show that delay and ionized inner shell mechanisms require electron-electron correlations among the four electrons, and are responsible for the second increase in the double-ionization probability. Furthermore, we show that our theoretical prediction about the relative prominence of certain double ionization mechanisms is in agreement with experimental results on the relative prominence of non-first- over first-order mechanisms.