Communication: the rotational excitation of D2 by H: on the importance of the reactive channels.

We report fully-quantum time-independent calculations of cross sections and rate coefficients for the collisional excitation and dissociation of D(2) by H, two astrophysically relevant processes. Our calculations are based on the recent H(3) global potential energy surface of Mielke et al. [J. Chem. Phys. 116, 4142 (2002)]. Results of exact three-dimensional calculations, i.e., including the reactive channels, are compared to pure inelastic two-dimensional calculations based on the rigid rotor approximation. A reasonable agreement is found between the two sets of inelastic cross sections over the whole energy range 10-9000 cm(-1). At the highest collisional energies, where the reactive channels are significant, the rigid rotor approach slightly overestimates the cross sections, as expected. At moderate collisional energies, however, the opposite behaviour is observed. The rigid rotor approach is found to be reliable at temperatures below ~500 K, with a significant but moderate contribution from reactive channels.