Temperature Dependence of the Vibrational Relaxation Rate Constants of CO2 (0001) in Binary Mixtures

The rate constants of intramolecular intermode relaxation of the CO2 molecule (0001) in pure CO2 and in binary mixtures with He, Ar, H2, O2, N2, CO, NO, N2O, and H2O were measured in the temperature range 300–1000 K by means of a laser-induced luminescence method. It is shown that these relaxation rate constants K for all the gas mixtures investigated increase with increase in the gas temperature in this range; the most efficient in deactivation of the 0001 level are the collisions of CO2 molecules with H2O molecules; the mechanisms of relaxation of the 0001 level of CO2 and their channels depend not only on the temperature but also on the parameters of colliding particles; for each of the colliding partners of the CO2 molecules there is a certain temperature Tc above which the temperature dependence of K is coordinated with the Landau–Teller dependence, and, moreover, the simpler the structure of the colliding partner of the CO2 molecule, the higher the temperature Tc. Deviations from these dependences at temperatures T < Tc are attributed to the influence of intermolecular forces of attraction, change of relaxation channels, and formation of molecular clusters. For all the colliding partners of the CO2 molecules, the interaction radii are determined from the intermolecular potentials of interaction used in the theoretical model.