Photon emission spectra from submicron silver particles induced by an electron beam have been measured using a light detection system combined with a 200-kV transmission electron microscope. Multiple peaks appear in the spectra associated with collective plasmon excitations produced in the particles by the incident electrons. The wavelengths of these peaks are observed to shift towards larger values with increasing particle diameter, as predicted by Mie theory. Moreover, photon maps have been obtained in a scanning mode and they indicate that those peaks correspond to the multipole modes of electromagnetic oscillations in metallic spheres ͑Mie resonances͒. The spectral shape of the emission and the dependence on particle size, impact parameter, and electron energy are well explained from theoretical calculations of the photon emission probability derived from a fully retarded analytical treatment of the interaction of fast electrons with metallic spheres.
Light emission generated by a high-energy electron passing through surfaces, thin films and particles of several materials were studied using a light detection system combined with a transmission electron microscope with an accelerating voltage of 200 kV. A silver film with a rough surface gives rise to inhomogeneous intensity distribution in the photon maps, which is due to the coupling of light with the non-radiative surface plasmon mode through the surface roughness. In the case of a rough surface of a silver film with a granular structure, light is strongly emitted from a localized region with high polarization. The emissions from silver particles with various diameters were observed. The emission spectra show multiple peaks corresponding to the multipole modes of the electromagnetic oscillation in the spherical particle. The results can be explained well by the theory involving the retardation effect.
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