Electron impact excitation of H and He+.V. Differential cross sections for the excitation of the n=2 levels of atomic hydrogen at intermediate energies

Abstract

Differential cross section for electron impact excitation of the 2s and 2p states of atomic hydrogen have been calculated at all angles for energies of 50 to 200 eV in a distorted wave polarized orbital approximation (allowing for target distortion). The results are compared with other theoretical models, and the total n=2 excitation differential cross sections are compared with recent absolute experimental data of Williams and Willis. There is complete agreement at small and moderate angles, but the method underestimates the experimental results in the backward direction. It is argued that the inclusion of final-channel distortion effects will remedy this defect. The effect of target distortion on the 1s to 2p total cross section is discussed.