Excitation and charge transfer in low-energy hydrogen atom collisions with neutral oxygen

TL;DR

This paper investigates excitation and charge transfer processes in low-energy hydrogen-oxygen collisions, providing theoretical rate coefficients crucial for stellar spectral modeling and oxygen abundance determinations.

Contribution

It extends a previously developed asymptotic LCAO model to include excited hydrogen states and calculates rate coefficients for astrophysically relevant temperatures.

Findings

Charge transfer and excitation involving hydrogen 4s states have the highest rates.

Extended model shows no significantly high rates from excited hydrogen configurations.

Rate coefficients are provided for temperatures between 1000 and 20000 K.

Abstract

Excitation and charge transfer in low-energy O+H collisions is studied; it is a problem of importance for modelling stellar spectra and obtaining accurate oxygen abundances in late-type stars including the Sun. The collisions have been studied theoretically using a previously presented method based on an asymptotic two-electron linear combination of atomic orbitals (LCAO) model of ionic-covalent interactions in the neutral atom-hydrogen-atom system, together with the multichannel Landau-Zener model. The method has been extended to include configurations involving excited states of hydrogen using an estimate for the two-electron transition coupling, but this extension was found to not lead to any remarkably high rates. Rate coefficients are calculated for temperatures in the range 1000 - 20000 K, and charge transfer and (de)excitation processes involving the first excited S-states, 4s.5So and 4s.3So, are found to have the highest rates.