Energy transfer as a function of collision energy. IV. State-to-state cross sections for rotational-to-translational energy transfer in HF+Ne, Ar, and Kr

Abstract

State-to-state cross sections for rotationally inelastic collisions of HF (v,J) with Ne, Ar, and Kr have been measured. Laser pumping of the molecular beam to the initial states v = 1, J = 1–6, and v = 2, J = 2, followed by infrared fluorescence, permitted measurements of relative cross sections with ‖ ΔJ ‖⩽8. The collision energy was varied between 4 and 16 kcal/mol. These cross sections could be fitted well using an inverse-power dependence on the rotational energy gap [due to Pritchard and co-workers; J. Chem. Phys. 70, 4155 (1979)] for rotational energy transfers of up to 55% of the initial translational energy. The energy-corrected sudden approximation was used to determine an ’’effective’’ collision length for rotationally inelastic scattering. The scattering is thought to occur predominantly on the repulsive wall of the intermolecular potential, except for the J = 1→J′ = 0 transition, which is shown to be sensitive to the depth of the van der Waals attractive well.