Surface-plasmon excitation during aloof scattering of low-energy electrons in micropores in a thin metal foil

A novel technique is used in studying the energy-loss spectrum of aloof (nontouching) electrons with surfaces. Metallic foils perforated by microchannels restrict the maximum impact parameter to the channel radius (20-200 nm). The passage of electrons (20-2000 eV) near the cylinder walls results in prominent energy-loss structure. In silver, a resonance loss peak at 3.5-3.6 eV is attributed to the formation of surface plasmons on the silver channels. The problem is modeled by a classical calculation of a charge moving parallel to a plane surface whose response is given by tabulated optical properties. The differential probability is calculated with the assumption that the lower limit to the impact parameter is determined by surface roughness. The calculations are compared with the experimental data.