Electron-energy-loss spectroscopy of plasmon excitations in concentric-shell fullerenes

We report evidence for surface plasmon excitations in concentric-shell fullerenes. A film of these concentric- shell fullerenes with radii around 5-7 nm produced by carbon bombardment of a silver polycrystalline target and measured by electron-energy-loss spectroscopy (EELS) in reflection geometry. These data were analyzed with the help of a dielectric theory developed for EELS in transmission geometry. Taking into account the concentric-shell-substrate interaction, the spectral shape can be explained as a combination of contributions from sigma-pi* interband transitions (around 13.5 eV), from the surface radial (sigma-pi*) and tangential (sigma-sigma*) plasmons (around 14.5 eV and 16.7 eV, respectively), and from the volume plasmon (24.5 eV). [S0163-1829(99)03107-0].