Determining the anisotropic interaction potential of D2Ar from rotationally inelastic cross sections

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Abstract
In a crossed molecular beam experiment, time‐of‐flight distributions of oD2 molecules scattered from Ar have been measured in a center‐of‐mass angular range from 50° to 100° at a collision energy of E=85 meV. The data show clearly resolved 0→2 rotational transitions of D2 in the backward direction. From a combined analysis of these inelastic cross sections and the measured total differential cross sections for D2+Ar at E=83 meV, the complete repulsive potential surface is derived. Comparison with the potential which LeRoy and Carley determined from spectroscopy shows that the repulsive part of its anisotropic V2 term is steeper, whereas the isotropic parts V0 agree within the experimental error. A combined analysis of the present inelastic scattering data and the original spectroscopic data yields an improved version of the three‐dimensional stretching‐dependent potential surface of LeRoy and Carley. Cross sections calculated from the semiempirical ‘‘HFD’’ potentials reported by Tang and Toennies and by Rodwell and Scoles are also fairly close to experiment, with the latter potential performing somewhat better than the former. The comparison with other hydrogen molecule–rare gas interactions reveals a maximum in the effective strength of the repulsive anisotropy for Ne–H2 and a nearly complete conformality of the reduced V0 and V2 terms to each other for He, Ne, and Ar–H2.

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