Anti-alignment driven dynamics in the excited states of molecules under strong fields

TL;DR

This paper introduces two models to study anti-alignment dynamics in excited states of molecules under strong fields, revealing dissociation behavior and challenging the idea of excited state stabilization.

Contribution

The paper presents novel quantum-mechanical and semi-classical models for H$_2^+$ and its isotopes to analyze anti-alignment and dissociation under strong fields.

Findings

Molecules dissociate at perpendicular angles to the field in excited and ground states.

Quantum dispersion leads to full dissociation of the initial state.

Bond-hardening stabilization in excited states is unlikely under strong fields.

Abstract

We develop two novel models of the H$_2^+$ molecule and its isotopes from which we assess quantum-mechanically and semi-classically whether the molecule anti-aligns with the field in the first excited electronic state. The results from both models allow us to predict anti-alignment dynamics even for the HD$^+$ isotope, which possesses a permanent dipole moment. The molecule dissociates at angles perpendicular to the field polarization in both the excited and the ground electronic state, as the population is exchanged through a conical intersection. The quantum mechanical dispersion of the initial state is sufficient to cause full dissociation. We conclude that the stabilization of these molecules in the excited state through bond-hardening under a strong field is highly unlikely.