Radiative association of atomic and ionic carbon

TL;DR

This paper calculates cross sections and rate coefficients for the formation of C$_2^+$ via radiative association, providing data relevant for astrochemical models at temperatures as low as 100 K.

Contribution

It offers new molecular data and quantum-mechanical calculations for C$_2^+$ formation, extending the temperature range and providing analytical fits for astrochemical use.

Findings

Rate coefficient at 100 K is about 2×10⁻¹⁸ cm³/s

Extended molecular data for low-lying states of C₂⁺

Provided analytical fits for reaction rates

Abstract

We present calculated cross sections and rate coefficients for the formation of the dicarbon cation (C$_2^+$) by the radiative association process in collisions of a C$(^3P)$ atom and a C$^+(^2P^o)$ ion. Molecular structure calculations for a number of low-lying doublet and quartet states of C$_2^+$ are used to obtain the potential energy surfaces and transition dipole moments coupling the states of interest, substantially increasing the available molecular data for C$_2^+$. Using a quantum-mechanical method, we explore a number of allowed transitions and determine those contributing to the radiative association process. The calculations extend the available data for this process down to the temperature of 100 K, where the rate coefficient is found to be about $2\times 10^{-18}$ cm$^3$/s. We provide analytical fits suitable for incorporation into astrochemical reaction databases.