Vibrational relaxation in H-H2 collisions

We present the results of quantum mechanical calculations of the rate coefficients for vibrational relaxation upsilon = 1 --> 0 of H-2 in H in the temperature range 300 less than or equal to T less than or equal to 4500 K. The results were obtained using two recent and independent calculations of the H-H-2 potential. for comparison purposes. Although reactive scattering is excluded from the present study, the results of quasi-classical trajectory calculations which include this process am used to estimate its contribution. The total rate coefficient which is thus obtained is found to be an order of magnitude smaller than that measured by Heidner and Kasper, but it is two orders of magnitude larger than the corresponding values for vibrational relaxation in He or H-2. The need for fresh experimental study is emphasized.