Positronium atom scattering by H2 in a coupled-channel framework

The scattering of ortho-positronium (Ps) by H2 has been investigated using a three-Ps-state (Ps(1s, 2s, 2p)H2 (X1 Σg+)) coupled-channel model and using the Born approximation for higher excitations and ionization of Ps and B1 Σu+ and b3 Σu+ excitations of H2. We employ a recently proposed time-reversal-symmetric non-local electron-exchange model potential. We present a calculational scheme for solving the body-frame fixed-nuclei coupled-channel scattering equations for Ps-H2, which simplifies the numerical solution technique considerably. Ps ionization is found to have the leading contribution to target-elastic and all target-inelastic processes. The total cross sections at low and medium energies are in good agreement with experiment. (author)