On the accuracy of semiclassical treatments of differential scattering of electrons by atoms: 1s-2s and 1s-2p excitation in e-H collisions

Abstract

Semiclassical formulae for the scattering amplitude are discussed and used to calculate the differential cross sections and the orientation and alignment parameters ( gamma and chi ) for 2s and 2p excitation in e-H(1s) collisions. The calculations are close-coupled, include only the 1s, 2s and 2p states and neglect exchange; they are made for impact energies 30.6, 54.4 and 100 eV and for scattering angle theta up to 60 degrees . For theta <or approximately=10 degrees , the agreement between the semiclassical and quantal results is good and improves systematically as the energy increases. For larger theta , the agreement is poorer and is no better at 100 eV tan at 54 eV. For gamma and chi , the agreement is significantly poorer than for the differential cross sections. Except for theta <or approximately=10 degrees , modification of the ordinary impact-parameter method to allow for differing wavenumbers does not improve the results significantly.