Ileceivcd I6 March 1071 The angular dcpendencc of electron scattering from the helium atom and the hydragcn molecule for small scattering angles in the 34 -100 eV impact energy range is explained in terms of the first Born approximation and the polnrizcd Uorn approximation. The thcorctical results compnrc favornbly \vith the expcrimentnl clntn for both elastic and inelastic scattering. New cxperimcntal and theorcticnl ccsults arc presented.
In this article we report some conclusions OS a comparison between theory and experiment for the angle dependence of electron scattering differential cross sections in the intermediate energy range. We find that the model outlined here may be used succeGGfully to describe electronimpact scattering processes at small scattering angles 9 5 400 in the energy range (E-AE) 2 15 eV, where E is the impact energy and AE is the threshold energy. Some processes (e.g., singlet-triplet excitation) occur solely by an electron exchange process; however, for the processes of interest in the present article, electron exchange may be neglected in the first cpproximation in this B, 0 range. The electron collision process may be envisioned as the electron polarizing the target and scattering off the polarized target. For intermediate and high energies and small scattering angles, the scattering off * A preliminary account of this research was given nt the 1970 June Meeting of the American Physical Society in Winnipeg [ 11.