Inelastic scattering calculations in polyatomic systems using an ab initio intermolecular potential energy surface. II. Rotational energy transfer in CO₂-H₂ collisions

Abstract

Results of quasiclassical trajectory studies of CO₂ (J_i=0, 16, 30)-H₂ (J_i=0, 2) collisions at E_tot=0.1, 0.2 eV are reported in terms of state-to-state integral inelastic cross sections, first moments of energy transferred in excitation and de-excitation processes and C values which characterize the variation of the rotational suprisal with energy gap between initial and final states. The magnitude of the first moments are shown to increase with increasing translational energy T_i and with the initial rotational state J_i^CO₂. The value of C decreases with increasing T_i. It is found to be strongly dependent upon J_i^CO₂ but depends only weakly upon J_iH₂. Comparison of our results with those of Preston and Pack for the CO₂-He and CO₂-Ar systems reveals that although the qualitative dependence of σ₋, σ₊, σ, <ΔE₋> and <ΔE₊> upon T_i and J_i^CO₂ is the same in all three systems, there are quantitative differences which reflect the atomic (molecular) size of He, H₂, and Ar. Furthermore, the suprisal parameter is distinctly different for all three collision partners (decreases in the order H₂, He, Ar) even when the "linear sum rule" holds, contrary to an earlier proposal by Procaccia and Levine that the surprisal parameter C would be independent of the nature of the collision partner.