Vibrational-rotational energy transfer in H-2-H-2 collisions II. The relative roles of the initial rotational excitation of both diatoms

A recently proposed [J. Chem. Phys. 111 (1999) 2401] new semi-classical dec oupling procedure for rotational projection states in ro-vibrationally inel astic atom-diatom and diatom-diatom collisions is extended and applied to i nelastic collisions in molecular hydrogen. The role of initial rotational e xcitation of both collision partners in the ro-vibrational transitions, att ached to the vibrational (10 --> 00) transition in para-H-2, is analyzed in detail. The computed vibrational self-relaxation rate constant for para-H- 2, is in a good quantitative agreement (within a factor of 2) with experime ntal data over the whole experimentally investigated temperature range, 50- 3000 K. (C) 1999 Elsevier Science B.V. All rights reserved.