Morse-6 Hybrid Potentials for Pair Interactions of Rare Gas Atoms

Abstract

Hybrid pair potential functions are constructed from three parts: (1) a short-range exponential repulsion of the form A exp (−λr), obtained from either Self-Consistent-Field or Thomas-Fermi-Dirac calculations; (2) a long-range dipole-dipole dispersion attraction −C6r−6 where the C6 coefficients are obtained from highly accurate semiempirical estimates; (3) a Morse potential A exp (−λr) −B exp (−λr/2), whose B parameter is found by fitting experimental second virial coefficients, and which is used to connect the long- and short-range segments. The bowls of the resulting potentials depend most perceptibly on the nature of the repulsive limb from which they are constructed. Potentials are constructed which describe He–Ne, He–Ar, Ne–Ne, Ne–Ar, Ar–Ar, Ar–Kr, Kr–Kr, and Xe–Xe interactions. The vibrational energy eigenvalues and spectroscopic constants are determined for these potentials. Comparison with the available experimental spectroscopic data and low energy molecular beam results is presented. Our most likely Morse-6 hybrids for ArAr, for example, give good agreement with molecular beam measurements, with the Tanaka and Yoshino spectroscopic measurements, and with the very flexible Barker-Pompe-Bobetic empirical potential.