Elastic scattering of electrons from ions

First experimental results are reported for high angle elastic scattering of electrons from an ion at collision energies below the inelastic threshold. Absolute partial cross sections have been measured for the angular range π 2-π for Ar⁺ over the energy range 4.0-7.0 eV. The results are compared to predictions of the classical Rutherford formula, and to a Born calculation using a screened nuclear potential. It is found that allowance for electron screening of the ionic core gives much better agreement with experiment. The application of such measurements of low energy backscattering from ions of various charge states as a sensitive test of many-body theory is discussed.