Radiative cooling of H3O+ and its deuterated isotopologues

TL;DR

This study provides a theoretical analysis of the radiative lifetimes and cooling functions of hydronium ions and their isotopologues, identifying long-lived states that could influence astrophysical and chemical processes at low temperatures.

Contribution

It introduces ab initio calculations of energy levels and transition rates for H3O+ and isotopologues, revealing long-lived metastable states and their potential for population trapping.

Findings

Identification of the longest-living ro-vibrational states.

Estimated radiative lifetimes for temperatures below 200 K.

Discovery of metastable states capable of population trapping.

Abstract

In conjunction with ab initio potential energy and dipole moment surfaces for the electronic ground state, we have made a theoretical study of the radiative lifetimes for the hydronium ion H$_3$O$^{+}$ and its deuterated isotopologues. We compute the ro-vibrational energy levels and their associated wavefunctions together with Einstein coefficients for the electric dipole transitions. A detailed analysis of the stability of the ro-vibrational states have been carried out and the longest-living states of the hydronium ions have been identified. We report estimated radiative lifetimes and cooling functions for temperatures $<$ 200 K. A number of long-living meta-stable states are identified, capable of population trapping.