Rovibrational relaxation in collisions between H2 molecules:: II.: Influence of the rotational state of the perturber

We have computed cross sections and rate coefficients for rovibrational transitions in ortho- and para-H-2, induced by ground state (v = 0, J = 1) ortho-H-2. These results complement our previous calculations relating to excitation by para-H-2 (v = 0, J = 0). The cross sections are found to be insensitive to the rotational state of the perturber. Discrepancies with measurements of the rate coefficient for v = 1 --> 0 vibrational relaxation at low temperatures persist. The value of this rate coefficient at low temperatures is shown to be determined by a combination of the Wigner threshold law and the presence of a quantal interference minimum. Further experimental and theoretical work on the H-2-H-2 system is called for in order to resolve the remaining discrepancies.