Interaction of Two Metastable Triplet Helium Atoms

Abstract

Ab initio quantum‐mechanical calculations have been performed for the ${}^5{\Sigma }_g^{+}$ , ${}^3{\Sigma }_u^{+}$ , and ${}^1{\Sigma }_g^{+}$ states arising from the interaction of two ${\text{1s2s}}^{3}S$ helium atoms. A rigorous upper bound to the quintet potential was found by use of the variational principle. Crude estimates of the autoionizing singlet and triplet states were obtained by the “stabilization” method. The quintet‐state potentials exhibit a van der Waals minimum, and the triplet and singlet potentials exhibit more substantial minima. The behavior of the wavefunctions in the separated‐atom limit was studied, and the range of applicability of the effective Heisenberg spin Hamiltonian was tested on the calculated potentials.