EFFECT OF ELECTRON-EXCHANGE IN POSITRONIUM-HYDROGEN SCATTERING

The elastic and inelastic scattering of ortho-positronium (Ps) by the hydrogen atom have been investigated using a three-Ps-state close-coup ling approximation. The higher (n greater than or equal to 3) excitati ons and ionization of the Ps atom are treated within the framework of the Born approximation. In both cases the effect of electron exchange has been included by a parameter-free nonlocal model potential derived from an antisymmetrization of the wavefunction followed by the remova l of nonorthogonality. Calculations are reported of scattering lengths ,phase shifts, and of elastic, Ps excitation, and total cross sections . The trend of present target elastic total cross section agrees quali tatively with available experimental results on Ps-impact scattering.