Two-Photon Total Annihilation of Molecular Positronium

The rate for complete two-photon annihilation of molecular positronium Ps${}_2$ is reported. This decay channel involves a four-body collision among the fermions forming Ps${}_2$, and two photons of 1.022 MeV, each, as the final state. The quantum electrodynamics result for the rate of this process is found to be ${\mathrm{\Gamma }}_{P{s}_2\to \gamma \gamma }$ = 9.0 $\times {10}^{-12}$ s${}^{-1}$. This decay channel completes the most comprehensive decay chart for Ps${}_2$ up to date.