A rigid sphere approach to positron elastic scattering by noble gases, molecular hydrogen, nitrogen and methane

A simple potential model of a rigid sphere combined with an adiabatic dipole polarization (~r-4) is tested for positron-atom and positron-molecule elastic collisions. The numerical model, which is based on the analytical solution of radial Schrödinger equation for r-4 potential, depends solely upon the average dipole polarizability of the target and one adjustable parameter – the radius of a hard core. The validity of model is assessed by an extensive comparative study against numerous experimental cross-sections and theoretical phase-shifts of angular momentum partial waves for positrons scattered elastically by He, Ne, Ar, Kr, Xe, H2, N2 and CH4. In particular it is shown that this very simple approach can be used to model positron elastic collisions with targets characterized by moderate dipole polarizabilities (Ar, Kr, H2, N2) in good agreement with experiments for impact energies covering almost entire range from the positronium formation threshold down to the zero energy