Abstract
This paper reports a study of surface plasmon excitation on the flat, oxide-covered aluminum surface, using high energy electrons which pass the surface at a finite, and sometimes large, impact parameter. The scattering probability dependence on impact parameter agrees qualitatively with classical, quasi-static calculations, which assume that the materials are characterized by homogeneous dielectric constants. A broad intensity maximum near 16 eV is identified as a surface plasmon made possible by the frequency dependence of the aluminum oxide dielectric constant.