# Radiative association of C(${}^3P$) and H${}^+$: Triplet states

## TL;DR

This study calculates the cross sections and rate coefficients for the radiative association of C(${}^3P$) and H${}^+$, revealing significantly higher rates than previous models and confirming the minor role of triplet states in CH${}^+$ formation.

## Contribution

It provides detailed quantum-mechanical calculations of cross sections and rate coefficients for triplet-state radiative association of C and H${}^+$, a novel analysis in this context.

## Key findings

- Rate coefficients are about 100 times larger than those for C${}^+({}^2{P^o})$ and H.
- Formation of CH${}^+$ via triplet c${}^3 ext{Σ}^+$ state is minor.
- Potential energy curves and transition dipole moments are accurately calculated.

## Abstract

The radiative association of C(${}^3P$) and H${}^+$ is investigated by calculating cross sections for photon emission into bound ro-vibrational states of CH${}^+$ from the vibrational continua of initial triplet d$\,{}^3\Pi$ or b$\,{}^3\Sigma^-$ states. Potential energy curves and transition dipole moments are calculated using multi-reference configuration interaction (MRCI) methods with AV6Z basis sets. The cross sections are evaluated using quantum-mechanical methods and rate coefficients are calculated. The rate coefficients are about 100 times larger than those for radiative association of C${}^+({}^2{P^o})$ and H from the A$\,{}^1\Pi$ state. We also confirm that the formation of CH${}^+$ by radiative association of C${}^+({}^2{P^o})$ and H via the triplet c$\,{}^3\Sigma^+$ state is a minor process.