Relativistic corrections for positronium–atom complexes

The Breit–Pauli Hamiltonian for many-electronic positron- and positronium–atom complexes is considered and is applied to the neutral positronium–atom complexes PsB–PsF, PsAl–PsCl, PsGa–PsBr, and PsIn–PsI. For these complexes, energy differences between the high- and low-spin states which arise from different positronic spin coupling schemes are estimated, and relativistic corrections for the dissociation energies into a positronium and a neutral atom. The relativistic effects are obtained from first-order perturbation theory based on the Hartree–Fock description. The influence of correlation effects on the dissociation energies for positronium halides are also discussed.