Configuration-interaction-Hylleraas calculations on one-positron atomic systems

Abstract

The suitability of the variational configuration-interaction-Hylleras method in obtaining accurate energies and annihilation rates for one-positron atomic systems is discussed. The wavefunctions are expanded in terms of configurations which consist of antisymmetrized products of r_ij^v coordinates (v=0, 1, 2) with Slater-type orbitals. Using 84, 84, 67 and 68 term wavefunctions the authors have obtained energies for the ^1,2S(Li;e⁺), ^1,2S(He^-;e⁺), ^2,3S(He;e⁺) and ^2,1S(H^-;e⁺) systems. The ^1,2S(Li;e⁺), ^1,2S(He^-;e⁺) and ^2,3S(He;e⁺) systems are stable with respect to positron dissociation but probably unstable with respect to positronium dissociation. With a view to facilitating further variational studies on atom-positron systems, a detailed discussion is given of the relative importance, on both annihilation rates and energies, of the configurations in the wavefunctions which represent particular correlation effects.