Quantal coupled channels calculations of the rates of self-relaxation of ortho- and para-H-2

We have computed thermally averaged rate coefficients for vibrational self- relaxation nu = 1 --> 0 of ortho- and para-H-2. The quantum mechanical, cou pled channels method was employed, with bases which are adequate to ensure convergence of the results at the kinetic temperatures (T = 300 and 500 K) considered. Although the inclusion of excited rotational states of the pert urber molecule leads to increases in the rate coefficients for vibrational relaxation, these increases are insufficient to reconcile the theoretical r esults with experimental measurements.