Abstract
Analyses the elastic scattering of electrons and positrons by atomic hydrogen at intermediate energies (50-500 eV) by using the basic ideas of the eikonal-Born series method to construct from first principles a local third-order optical potential. In addition to the first-order (static) interaction, the authors' optical potential contains a complex second-order part, obtained from improved values of the second Born approximation to the scattering amplitude, and also the leading contribution of the third-order part. Exchange effects are taken into account by means of a local pseudopotential. A full wave treatment of the optical potential is then performed, and a detailed comparison is made with recent absolute measurements of e--H differential cross sections. Total (integrated) elastic and total (complete) cross sections for both electron and positron impact are also discussed.