Fine-structure resolved rotational transitions and database for CN+H-2 collisions

Cross sections and rate coefficients for CN + H-2 collisions are calculated using the coupled states (CS) approximation. The calculations are benchmarked against more accurate close-coupling (CC) calculations for transitions between low-lying rotational states. Comparisons are made between the two formulations for collision energies greater than 10 cm(-)1. The CS approximation is used to construct a database which includes highly excited rotational states that are beyond the practical limitations of the CC method. The database includes fine-structure resolved rotational quenching transitions for v = 0 and j <= 40, where v and j are the vibrational and rotational quantum numbers of the initial state of the CN molecule. Rate coefficients are computed for both para-H-2 and ortho-H-2 colliders. The results are shown to be in good agreement with previous calculations, however, the rates are substantially different from mass-scaled CN + He rates that are often used in astrophysical models.