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 $\Gamma_{Ps_{2} \rightarrow \gamma\gamma}$ = 9.0 $\times 10^{-12}$ s$^{-1}$. This decay channel completes the most comprehensive decay chart for Ps$_{2}$ up to date. 
Jes\'us P\'erez-R\'ios, Sherwin T. Love and Chris H. Greene
physics.atom-ph astro-ph.HE hep-ph physics.chem-ph