Temperature dependence of the rate coefficient of formation of CN radical from C + NH.

[Display omitted] • Unprecedented exhaustive QCT calculations have been carried out in the range 5–800 K. • Rate coefficients fall rapidly from 5 K to 150 K and then level-off. • The abrupt decrease is mainly due to the electronic degeneration factor. • Cross sections and rate coeffcients are very sensitive to the rotational excitation of NH. • Two capture models based on the long-range interaction have been developed. Rate coefficients of the complex-forming C + NH → H + CN reaction have been calculated at temperatures ranging from 5 K to 800 K using quasi-classical trajectories on a potential energy surface which accurately describes the attractive long-range interaction, along with results using two capture models. In contrast with the constant value recommended in astrochemical databases, a steep decrease of the rates has been found up to 150 K, and then they tends to be nearly constant. Such behavior is analyzed in terms of the rovibrational state-selected rate coefficients and cross sections singling out the role played by the rotational excitation of the initial diatom. The effect of the electronic degeneracy is also discussed. [ABSTRACT FROM AUTHOR]