Variational calculations of the ground state energy of 4He trimers are reported and are compared with the Hall-Post-Stenschke lower bound on the ground state energy. The variational result for the ground state energy for a range of model pair potentials is in the range −0.05 to −0.2 K; the effect of the triplet nonadditive term is estimated to be less than 1% of the contribution of the pair potentials. A study of the variation of the ground state energy of 3 bosons with pair potential coupling constant is also reported for a Lennard-Jones and a Morse potential model. There is no bound spin 3/2 3He trimer; a lower bound is given for the ground state energy of the spin 1/2 trimer and analogy with the boson results is used to argue that the spin 1/2 trimer is probably not bound. This paper contains computational applications of formal results derived elsewhere.

Parameter adjustments in a family of semiempirical potentials are reported. The result is a two-parameter potential incorporating theoretically determined dipole–dipole and dipole–quadrupole interactions which fits dilute helium gas data to within 6% over the temperature range 1–2000°K. The data fits near 50°K are not fully satisfactory, nor is the fit of viscosity data below 4°K. The sensitivity of the calculations to the inclusion of the dipole–dipole interaction for properties below 4°K is studied. The calculations using quantum mechanics show a greater sensitivity in the virial coefficient than the viscosity and differ from calculations using classical mechanics. The semiclassical limits of the calculations are discussed.

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The effects of interactions between the outgoing nucleons on the cross sections for the inelastic electrondeuteron scattering process e-\-d-^ e-j-p-j-n are examined in detail. Results are presented as corrections to the theoretical cross sections which were calculated in a previous paper with a relativistic theory but neglecting final-state interactions. The changes are significant for the determination of the electromagnetic form factors of the neutron from the experimental cross sections. The method of the paper follows the treatment of final-state interactions given by Durand, extended to include the D state of the deuteron and the coupling between final-state partial waves of the same total angular momentum and parity. The resulting expressions for the quasielastic peak cross sections are expected to be valid in the momentumtransfer range 0

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.