Positron annihilation in the bipositronium Ps2

The (e-,e+)-pair annihilation in the bipositronium Ps2 (or e-e+e-e+) is considered. In particular, the two-, three-, one-, and zero-photon annihilation rates are determined to high accuracy. The corresponding analytical expressions for these annihilation rates are also presented. By using our most recent and accurate variational wave functions produced for the ground S(L=0) state of the bipositronium Ps2 (E=-0.516 003 7754 a.u.) we have found for the two-photon annihilation rate Γ2γ≅4.664 24x109 s-1, while Γ3γ(Ps2)≅1.2022x106 s-1, Γ1γ≅1.954x10-1 s-1, and Γ0γ≅2.34x10-9 s-1. Also, a large number of bound state properties have been determined for this system