Positron-argon elastic, positronium formation and ionizing collisions at 60°

The energy dependencies of the differential cross sections for elastic scattering, positronium formation and direct single ionization in positron-argon collisions at 60° are reported in the energy range 40-150 eV. Of particular interest is the region from 55-60 eV, where earlier measurements by Dou and co-workers found a drop in the elastic scattering cross section by a factor of two. This structure was tentatively attributed to a cross-channel coupling effect with an open inelastic scattering channel. No structure has been found in the three differential cross sections presented herein.