Optical potential approach for positron scattering by metastable 2³S state of helium

The momentum space coupled channels optical (CCO) method for positron scattering has been extended to study the scattering of positrons by metastable helium for impact energies in the range from the positronium threshold up to high energies. Both the positronium formation and ionization continuum channels are included in the calculations via a complex equivalent local potential. The positronium formation, ionization, elastic and 2³S-2³P excitation, and total scattering cross sections are all presented and compared with the available information.