Two-potential eikonal approximation for electron-atom collisions

The Glauber approximation is known to be in appreciable error at all angles when applied to the elastic electron-atom scattering at medium and lower energies. It is shown that this is not due to the frozen-target approximation but mainly a result of the inadequate semiclassical treatment of close-encounter collisions in the Glauber approximation. A simple method is proposed to correct this inadequacy and is applied to $e$-H elastic scattering at energies from 20 to 100 eV. A remarkable improvement over the Glauber approximation is obtained, and the results agree with experiments very well at all angles where measurements are available.