The Bohm-Pines electron plasma theory is employed to give a theoretical interpretation of some experimental results of Marton et al. on the scattering of 20-kev electrons by a thin gold foil. General criteria are presented which can in principle select in any given case between the alternative mechanisms of collective excitation or one-electron excitation. For the general case of collective excitation the scattering law is derived and used in a numerical analysis of the experimental data. Agreement with the Bohm-Pines theory is satisfactory.

• Received 3 August 1955

DOI:https://doi.org/10.1103/PhysRev.101.554