Semiempirical Potential and Bound State of the Helium−4 Diatom

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Abstract
Hybrid potentials for the 4He–4He system composed of the theoretical short‐range repulsion, an empirical potential at the minimum, and the theoretical long‐range attraction have been constructed. Second virial coefficients calculated for these potentials are in poor agreement with experimental data. A semiempirical potential is constructed which fits the data well. This potential becomes the theoretical interaction at large separations; its gross features are a core radius of 2.645 Å and a potential minimum of −1.73×10−15 erg at 2.975 Å. There is one weakly bound state of the helium−4 diatom with a binding energy of roughly 0.01°K. An analysis of the effect of uncertainties in the experimental data upon these results is included; the bound state remains even with the allowed uncertainties.