Formation of the simplest stable negative molecular ion H3- in interstellar medium

TL;DR

This paper explores the formation of the H3- ion in space, analyzing its properties and suggesting methods for its detection, which could reveal the presence of H- ions in the interstellar medium.

Contribution

It provides the first detailed theoretical analysis of H3- formation, structure, and potential observability in the interstellar medium.

Findings

H3- can form via radiative association in space environments.

Computed properties of H3-, including dipole moment and vibrational states.

Proposed detection methods for H3- in interstellar observations.

Abstract

We present the theory of radiative association of atoms and molecules, and we apply it to the (H$_2$-H$^-$) van der Waals complex. We discuss the possibility for the H$_3^-$ ion to be formed in the interstellar medium in an environment with abundant ionized molecular hydrogen H$_2^+$. The observation of H$_3^-$ would also be a probe for the presence of H$^-$ in the interstellar medium. By computing the electronic structure of the H$_3^-$ ion, we determine its dipole moment, bound states, rotational constants, predissociated vibrational resonances and their lifetimes, and suggest a way to detect the ion in the interstellar medium.