An calculation of positron - hydrogen scattering at intermediate energies

Calculations of positron - hydrogen scattering at intermediate energies up to a maximum energy of 6.0 Ryd are performed using the close-coupling (CC) approach. A large basis of positron - hydrogen channels (28 states) is supplemented by the Ps(1s), Ps(2s) and Ps(2p) channels. The inclusion of the positronium states in the CC expansion leads to a model which can describe most of the physics of the positron - hydrogen system with a reasonable degree of accuracy. In particular, the positronium formation cross section, the total reaction cross section and the ionization cross section are all in agreement with experiment.