Multi-reference configuration interaction calculation of positronium fluoride 2,1S and 2,1P states

Multi-reference configuration interaction calculations for the ground state ^2,1S and an excited state ^2,1P of positronium fluoride (PsF) were performed, and their energies, the positronium (Ps) binding energies and the two-photon positron-electron pair annihilation rates were presented. From an analysis of the convergence pattern of the total energies and the two-photon annihilation rates with respect to the angular momentum of basis functions, an extrapolation method which may give accurate Ps binding energies and two-photon annihilation rates was applied. Estimated Ps binding energy for ^2,1S state of PsF was in good agreement with the recent reliable calculations. The structures of ^2,1S and ^2,1P states of PsF also were predicted from the point of view of the two-photon annihilation rate.