A Monte Carlo quasiclassical trajectory study of energy transfer in Ar+HF collisions

Abstract

Quasiclassical trajectories on a pairwise-additive potential-energy surface have been used to compute state-to-state cross sections for energy transfer in Ar+HF. Interest is focused upon relaxation from high vibration-rotation states. Pure-rotational energy transfer in excited vibrational states, vibrational relaxation, and the effect of relative translational energy on the energy transfer were also investigated. Most of the calculations were carried out for 1.0 eV relative translational energy. Initial vibrational states vi = 0, 2, 4, and 6 and initial rotational states Ji = 0, 10, 20, 30, and 40 were studied at this collision energy. The energy transfer for initial state vi = 4, Ji = 20 was studied at the initial relative translational energies 0.2, 0.4, 0.6, 0.8, and 1.0 eV. For collisions of Ar with highly excited HF the dominant energy transfer is V-R. The energy transfer results in an increase in the rotational state for downward vibrational transitions and a decrease in rotational state for upward vibrational transitions. The results suggest that pure-rotational energy transfer for low levels of rotational energy (Ji≲10), even in high vibrational states, should be accurately described by the rigid-rotor approximation. None of the energy transfer processes has a strong dependence on the initial relative translation energy, however, the influence is not negligible in all cases.