VIBRATIONAL-RELAXATION OF HIGHLY EXCITED CF2CL2 AND CF2HCL BY MONATOMIC GASES - DEPENDENCE ON ENERGY AND MASS

The relaxation of vibrationally excited CF2Cl2 and CF2HCl (the average energy, [E], ranged from 2000 to 30 000 cm-1) by rare gases was monit ored with time-resolved optoacoustics. Above 8000-10 000 cm-1, the col lision efficiency, beta, was independent of excitation energy and deac tivator: beta(CF2Cl2) = 1.7 x 10(-3) and beta(CF2HCl) = 1.5 x 10(-3). The average energy removed per collision, <<DELTAE>>, is linear with [ E]. For [E] < 8000-10 000 cm-1, beta decreases with decreasing energy; the energy dependence was similar for all deactivators. The present e xperiments suggest that the energy dependence of the observed k(VT) is due to an energy dependence on the microscopic rate coefficient for r elaxation and not the initial distribution of vibrational energy.