Elastic scattering of positrons with hydrogen and lithium atoms at intermediate energies

The elastic scattering of positrons with hydrogen atoms (energy range 200 to 500 eV) and with lithium atoms (energy range 60 to 400 eV) is studied in the framework of a two-potential approach. The incident particle distortion (both in the initial and final channels) and target polarization are considered. The results are compared with the other available calculations. A good agreement with some calculations based on third order optical potential method is obtained for higher energies.