Spontaneous radiative dissociation of the second bound state of positronium hydride

The spontaneous radiative dissociation spectrum of the second bound state of positronium hydride (PsH) located just below the H(2p) + Ps(2p) threshold energy is investigated by the variational and complex coordinate rotation methods. Convergence of the transition rates is examined in both length and velocity gauges. The spectrum indicates that the primary channel of radiative dissociation is the transition into the continuum of H(1s) + Ps(2p), and the secondary one is that into the H(2p) + Ps(1s) continuum. Radiative transition to the resonance state located close to the second bound state is found to exist. The total rate of the radiative dissociation is found to be 9.1(2) x 108 s-1.