A SEMICLASSICAL MODEL FOR POLARIZATION FORCES IN COLLISIONS OF ELECTRONS AND POSITRONS WITH HELIUM-ATOMS

A simple semiclassical model is proposed for the calculation of the po larization potential at short range where the impacting electron penet rates the electron cloud of the target atom. The new method is applied to the scattering of electrons and positrons from He atoms at energie s between 0.1 and 50 eV. The model is described in detail and is shown to produce a local effective potential which is computationally very easy to devise. Calculations for electron scattering are carried out f or the elastic integral cross sections and for angular distributions o f electrons at several collision energies and compared both with exper iments and with more sophisticated calculations. The agreement of the present results with experiments is invariably very good. Further test calculations for the positron scattering processes also agree very we ll with the available experiments and with other theoretical predictio ns.