Optical Potential Calculation for Positron Collision with Helium

The positron--helium system is studied with the momentum-space coupled-channel optical method. The positronium formation cross sections from the positronium formation threshold to 400eV and total cross sections from 17 to 3000eV are calculated. Ionization continuum and positronium formation channels are included via a complex equivalent-local optical potential in the
present calculations. The results are compared with the available experimental and theoretical data.