On the argon–methane interaction from scattering data

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Abstract
Total differential cross sections have been measured for Ar–CH4 at E=90.1 meV in the center of mass angular range from 5° to 55°. The well resolved rainbow maximum and the superimposed rapid oscillations are used to establish a reliable isotropic interaction potential V0(R). With this V0(R), the torque and low temperature second virial coefficients are analyzed to establish constraints on the anisotropic potential V3(R) which obeys tetrahedral symmetry. In a final step a complete potential surface is determined based on all three data sets. The scattering calculations are performed in the coupled-states approximation for rotational state-to-state transitions which are summed for the total differential cross section. Small variations of anisotropic parameters lead to dramatic changes in the inelastic differential cross sections, while only small effects are observed in the total differential cross section.