Trajectory studies of atomic recombination reactions. III. Energy transfer in bromine-inert gas systems

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Energy transfer in collisions of helium, argon, and xenon atoms with highly vibrationally excited bromine molecules is studied by computing 3D classical trajectories. Dissociation probabilities Pdiss are obtained as a function of the energy barrier Δ E/kT to be overcome. They vary approximately as Pdiss=P0(1+Δ E/kT)−4.5, and P0∝μ0.6 where μ is the reduced collision mass. Mean vibrational and rotational energy changes are calculated for systems in which the bromine molecules are initially in thermal rotational equilibrium but have varying degrees of vibrational excitation. The relative importance of vibration-rotation coupling at different vibrational energies is demonstrated. The order of collision numbers for rotational relaxation is He>Ar>Xe. The relative efficiencies of He, Ar, and Xe atoms in producing vibrational relaxation of Br2 vary with the initial degree of vibrational excitation.