Double Ionisation in R-Matrix Theory Using a 2-electron Outer Region

TL;DR

This paper introduces an extended R-matrix method with a two-electron outer region to accurately model double ionisation in helium, capturing both direct and sequential processes and aligning well with existing data.

Contribution

The paper presents a novel two-electron outer region within R-matrix theory for double ionisation, enabling detailed analysis of complex ionisation mechanisms.

Findings

Cross sections agree with established data.

Method identifies signatures of sequential double ionisation.

Provides insights into higher-order ionisation processes.

Abstract

We have developed a two-electron outer region for use within R-matrix theory to describe double ionisation processes. The capability of this method is demonstrated for single-photon double ionisation of He in the photon energy region between 80 eV to 180 eV. The cross sections are in agreement with established data. The extended RMT method also provides information on higher-order processes, as demonstrated by the identification of signatures for sequential double ionisation processes involving an intermediate He$^{+}$ state with $n=2$.