Isotope effect on the formation of CN by radiative association reactions

The formation of CN and its isotopologue (CN)-N-15 through radiative association has been investigated. We considered two processes for the collisions of ground state C(P-3) and N(S-4) atoms (A(2)Pi -> X-2 Sigma(+) and b(4)Pi -> a(4)Sigma(+)), as well as, for the first time, we investigated the radiative association of ground state C(P-3) and excited N(D-2) atoms (B-2 Sigma(+) -> X-2 Sigma(+)). The cross-sections for the three processes have been calculated using semi-classical, quantum mechanical, and Breit-Wigner theories. The rate constants, derived from the combination of semi-classical and Breit-Wigner results, have been fitted to the Kooij formula to be used in astrochemical modeling. The rate constant for the B-2 Sigma(+) -> X-2 Sigma(+) process dominates in the investigated temperature range (10-10 000 K), when its own asymptotic energy is used as a reference level. Moreover, the B-2 Sigma(+) -> X-2 Sigma(+ )process presents the most pronounced isotope effect on the rate constant. We suggest considering these newly investigated radiative association processes for the formation of CN and (CN)-N-15 in the interstellar medium. (c) 2024 Author(s).