A quantum mechanical calculation of the CN radiative association

Abstract

ABSTRACT Radiative association of CN is investigated through the quantum mechanical method, including the cross sections and rate coefficients. The ab initio potential energy curves, transition dipole moments, and permanent dipole moments of CN are obtained by the internally contracted multireference configuration interaction method with Davidson correction and aug-cc-pwCV5Z-DK basis set. For the collision of the ground state C (3Pg) and N (4Su) atoms, except for the four previously studied processes including the A2Π → X2Σ+, X2Σ+ → A2Π, A2Π → A2Π, and X2Σ+ → X2Σ+ transitions, four other radiative association processes including b4Π → a4Σ+, a4Σ+ → b4Π, b4Π → b4Π, and a4Σ+ → a4Σ+ transitions are considered. We also considered the collision of the excited C (1Dg) and the ground N (4Su) atoms including the 24Π → 14Σ− process and the collision of the ground C (3Pg) and the excited N (2Du) atoms including 22Π → B2Σ+, 32Π → B2Σ+, and 42Π → B2Σ+ transitions. The temperature population factor is considered to describe the thermal population of the three different dissociation asymptotic energies. The results show that the contribution of the A2Π → X2Σ+ and b4Π → a4Σ+ transitions to the total rate coefficients is significant over the entire temperature range. While considering the collision of C and N involving excited states, the contribution of the 22Π → B2Σ+, 32Π → B2Σ+, and 42Π → B2Σ+ transitions to the total rate coefficients cannot be ignored at the temperature range larger than 10 000 K. Finally, the rate coefficients are fitted to an analytical function for astrochemical reaction modelling.