Photodetachment and some rearrangement cross sections for the negative positronium ion

First theoretical estimates of cross sections for capture and detachment in collisions between protons and negative positronium ions are reported in the energy range 1-100 keV lab for the incident proton. Cross sections have been obtained for a one-active-electron model of Ps- introducing an effective potential for interactions between the outer electron and the positronium core in the system. In our calculations, we have applied the semiclassical formalism using a two-centre atomic orbital expansion with 22 states. In order to test the effective potentials, we have computed the photodetachment of Ps- and found that the present approximation is more accurate than the zero-range asymptotic model. A brief discussion of some further approximations made in this work is also given. (author)