Extreme correlation and repulsive interactions in highly excited atomic anions

TL;DR

This study investigates how highly excited atomic anions exhibit strong, sometimes repulsive, interactions affecting photodetachment cross sections, highlighting the role of near-degeneracies and permanent dipole moments in these processes.

Contribution

It provides a quantum mechanical analysis of partial cross sections in atomic anions, revealing the influence of near-degeneracies and permanent dipole moments on threshold behavior.

Findings

Non-Wigner threshold behavior observed in cross sections

Near-degeneracies significantly influence interaction dynamics

Permanent dipole moments drive the observed phenomena

Abstract

At high energies, single-photon photodetachment of alkali negative ions populates final states where both the ejected electron and the residual valence electron possess high angular momenta. The photodetached electron interacts strongly with the anisotropic core, and thus the partial cross sections for these channels display non-Wigner threshold behavior reflecting these large, and occasionally repulsive, interactions. Our fully quantum mechanical theoretical study enables a deeper interpretation of these partial cross sections. Comparisons of the behavior in different channels and between different atomic species - sodium, potassium, and cesium - show the critical role of near-degeneracies in the energy spectrum and demonstrate that much of the behavior of the partial photodetachment cross sections stems from the permanent, rather than induced, electric dipole moments of these nearly-degenerate channels. This provides a concrete example of a system where negative dispersion forces play a decisive role.