An inelastic scattering process is observed between 2.5 and 4.0 eV when clusters of 10- to 50-nm-diam aluminum spheres are excited by a 1-nm-diam probe of 100-keV electrons. This inelastic scattering is a maximum when the incident electron probe is positioned within 10 nm of the smaller of two touching spheres. The observed energy and the spatial variation of the scattering probability are consistent with a calculation for a two-sphere system immersed in aluminum oxide.

• Received 19 July 1982

DOI:https://doi.org/10.1103/PhysRevLett.49.936