CARS STUDIES ON THE HETEROGENOUS RELAXATION OF VIBRATIONALLY EXCITED HYDROGEN AND DEUTERIUM

Wall deactivation rates for H-2(nu = 1) -->(wall) H-2(nu = 0) and D2(nu = 1) -->(wall) D2(i = 0) were measured by probing the vibrationally excited molecules with coherent Anti-Stokes Raman spectroscopy. The probabilities for vibrational relaxation at room temperature were found to be gamma = (3.5 +/- 0.6) X 10(-3) for quartz, (1.2 +/- 0.2) X 10(-3) for pyrex. (1.1 +/- 0.2) X 10(-3) for HF-cleaned pyrex walls and (0.5 +/- 0.1) X 10(-3) for pyrex coated with highly fluorinated teflon. The temperature dependence of the heterogeneous relaxation was studied in the temperature range 188-300 K. The wall deactivation rate for quartz increases with increasing temperature according to gamma(T) = (5.9 +/- 1) X 10(-3) exp [ - (1 180 +/- 340) J mol-1/RT] for hydrogen and to gamma(T) = (6.7 +/- 1.1) X 10(-3) X exp [ - (1340 +/- 400) J mol-1/RT] for deuterium.