A comparison of the predictions of various model N2–He potential energy surfaces with experiment

Abstract

Predictions of beam scattering and bulk gas phenomena based upon five different model potential energy surfaces for the N2–He system are compared with experiment. The surfaces considered are our recent HFD1 and HFD2 surfaces based on the Hartree–Fock plus damped dispersion (HFD) model, the surface of Habitz, Tang, and Toennies (HTT) based upon the Tang–Toennies model, the surface of Keil, Slankas, and Kuppermann (KSK) and a modification (KKM3) of the KSK surface. The physical observables against which these surfaces are tested include total differential scattering cross sections, state-to-state inelastic differential scattering cross sections, interaction second virial coefficients, shear viscosity and binary diffusion coefficients, and the relaxation cross section for the Senftleben–Beenakker effect on the shear viscosity. None of the surfaces is in complete agreement with all of these observables. For the interaction second virial coefficients, the shear viscosity and binary diffusion coefficients, the HFD1 surface is the only one to predict values within most of the experimental error bars. The relaxation cross section is correctly predicted only by the KKM3 surface which was essentially fitted to it. The HFD1, HFD2, and HTT surfaces are all in good agreement with the state-to-state inelastic cross sections. The KSK surface gives the best agreement with the total differential cross section. It appears that an accurate N2–He surface cannot be obtained from simple models, and its determination will require multiproperty fits.