A four-body calculation of the radiative dissociation of excited positronium molecules

This study reports a four-body calculation of the radiative dissociation of positronium molecules ( Ps₂ Ps 2 ) in an excited state. The excited state of Ps₂ Ps 2 lies between the Ps ( $$n=1$$ n = 1 ) + Ps ( $$n=1$$ n = 1 ) and Ps ( $$n=1$$ n = 1 ) + Ps ( $$n=2$$ n = 2 ) thresholds and spontaneously dissociates into Ps ( $$n=1$$ n = 1 ) + Ps ( $$n=1$$ n = 1 ) through an electric dipole transition accompanied by photon emission. The energy spectrum and dissociation rates are calculated using a complex coordinate rotation method within the dipole approximation. The total radiative dissociation rate is 0.044\ ns⁻¹ 0.044 ns - 1 , which is one order of magnitude smaller than that of the electric dipole transition to the ground state of Ps₂ Ps 2 . The branching ratio of the radiative dissociation among the all spontaneous decay modes, including annihilation, has been determined to be 1.5%.