Time-dependent R-matrix theory applied to two-photon double ionization of He

TL;DR

This paper develops a time-dependent R-matrix method to accurately simulate two-photon double ionization of helium by intense XUV laser pulses, enabling precise cross section calculations and dynamic electron flow analysis.

Contribution

It introduces a generalized time-dependent R-matrix approach that combines detailed wavefunction descriptions with efficient propagation for double ionization processes.

Findings

Cross sections agree with existing data

Flow between inner and outer regions is accurately modeled

Method allows propagation over longer timescales

Abstract

We introduce a time-dependent R-matrix theory generalised to describe double ionization processes. The method is used to investigate two-photon double ionization of He by intense XUV laser radiation. We combine a detailed B-spline-based wavefunction description in a extended inner region with a single-electron outer region containing channels representing both single ionization and double ionization. A comparison of wavefunction densities for different box sizes demonstrates that the flow between the two regions is described with excellent accuracy. The obtained two-photon double ionization cross sections are in excellent agreement with other cross sections available. Compared to calculations fully contained within a finite inner region, the present calculations can be propagated over the time it takes the slowest electron to reach the boundary.