Radiative association of atomic and ionic nitrogen

Abstract

ABSTRACT Radiative association for the formation of molecular nitrogen cation ${\rm{N}}_2^ + $ during the collision of an N(4Su) atom and an N+(3Pg) ion is investigated. The corresponding cross-sections and rate coefficients are computed by the quantum mechanical method based on ab initio potential energy curves and transition dipole moments, which are obtained by the internally contracted multireference configuration interaction method with the Davidson correction and aug-cc-pCV5Z-DK basis set. A number of low-lying doublet, quartet, and sextet states correlating to the N(4Su) + N+(3Pg) dissociation limit are considered. Hence, we investigate a number of dipole-allowed transitions and determine their contributions to the radiative association. The results show that transitions originating in the f4Πu, D2Πg, ${{\rm{B}}^2}\Sigma _{\rm{u}}^ + $, ${{\rm{1}}^4}\Sigma _{\rm{g}}^{\rm{ + }}$, and ${{\rm{1}}^6}\Sigma _{\rm{u}}^{\rm{ + }}$states are the main contributors for the radiative association process. The calculated rate coefficients are valid for temperatures from 100 to 10 000 K and fitted to the analytical function suitable for astrochemical reaction applications.