Triple ionization and "frustrated" triple ionization in triatomic molecules driven by intense laser fields

TL;DR

This study develops a semi-classical model to analyze triple and 'frustrated' triple ionization in triatomic molecules under intense laser fields, revealing key ionization pathways, electron attachment preferences, and molecular fragmentation patterns.

Contribution

It introduces a novel 3D semi-classical approach that includes Coulomb singularities and criteria to accurately simulate multi-electron escape dynamics in triatomic molecules.

Findings

Two main pathways dominate 'frustrated' triple ionization.

The Rydberg electron prefers attachment to He$^{2+}$.

Fragmentation patterns indicate deviation from initial linear structure.

Abstract

We formulate a three-dimensional semi-classical model to treat three-electron escape dynamics in a strongly-driven linear triatomic molecule, HeH$_{2}^{+}$. Our model includes the Coulomb singularities. Hence, to avoid unphysical autoionization, we employ two criteria to switch off the Coulomb repulsive force between two bound electrons and switch it on when the motion of one electron is mostly determined by the laser field. We investigate triple and "frustrated" triple ionization. In the latter process two electrons escape while one electron remains bound in a Rydberg state. We find that two pathways prevail in "frustrated" triple ionization, as in "frustrated" double ionization. We also find that the electron that remains in a Rydberg state is more likely to be attached to He$^{2+}$ compared to H$^{+}$. Our results indicate that in triple and "frustrated" triple ionization electronic correlation is weak. Moreover, we compute the sum of the kinetic energies as well as the angular patterns of the final ion fragments in triple and "frustrated" triple ionization. These patterns suggest that the fragmenting molecule deviates from its initial linear configuration.