Rovibrational excitation of HD in collisions with atomic and molecular hydrogen

We have computed cross-sections and rate coefficients for rovibrational tra nsitions in HD, induced by collisions with atomic and molecular hydrogen. W e employed fully quantum-mechanical methods and the potential of Boothroyd et al. for H-HD, and that of Schwenke for H-2-HD. The rate coefficients for vibrational relaxation nu = 1 --> 0 of HD are compared with the correspond ing values for H-2 The influence of vibrationally excited channels on the r ate coefficients for rotational transitions within the nu = 0 vibrational g round state of HD is shown to be small at T = 500 K, where T is the kinetic temperature. The rate coefficients, for 100 less than or equal to T less t han or equal to 2000 K, are available from http://ccp7.dur.ac.uk/.