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[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]

Graphical abstract Highlights • Aimed at filling the gap in the theoretical studies of the CH 3 's photo-dissociation. • Our results look promising reproducing the same trend as state of the art experiments. • The method used allows the interpretation of the internal mechanisms of the process. Abstract The photodissociation dynamics of methyl radical from selected vibrational levels of the 3 s and 3 p z Rydberg states has been studied using the trajectory surface hopping method on one-dimensional potential energy curves along the carbon-hydrogen dissociative coordinate and the non-adiabatic couplings between them, calculated by ab initio methods. Lifetimes and product distributions have been obtained for all the studied vibrational levels and compared with previous theoretical and experimental works. The theoretical lifetimes tend to decrease as vibrational excitation increases in accordance with experimental results. The agreement, however, is only qualitative considering the reduced dimensionality of the model. [ABSTRACT FROM AUTHOR]