Distortion Effects in the Elastic Scattering of 100- to 400-eV Electrons from Helium

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Abstract
The elastic scattering of 100- to 400-eV electrons from helium is analyzed by explicit calculations of the scattering phase shifts including the effects of both adiabatic and non-adiabatic distortion of the target atom. The calculations involve numerical solution of the appropriate single-channel scattering equation for low angular momentum states and analytical estimation of the phase shifts for high angular momentum states of the scattering electron. The adiabatic and nonadiabatic distortion effects are represented by the appropriate central potentials derived in earlier works. Results of these calculations are compared with recent experimental data and other calculations. Atomic distortion causes the differential cross section to have a relatively high peak in the forward direction at all energies considered. The nonadiabatic corrections to the adiabatic polarization are required to sharpen and reduce this forward-scattering peak somewhat. As a whole, the inclusion of adiabatic and nonadiabatic distortion gives a rather good description of the differential scattering cross sections throughout the 100- to 400-eV range.