  A new type of excitations by highly focused electron beams in scanning
transmission electron microscopes is predicted for nanoparticles. The
calculated electron energy loss spectra of metallic (silver) and insulating
(SiO(sub2)) nanoplatelets reveal dramatic enhancement of radiative
electromagnetic modes within the light cone, allowed by the breakdown of
momentum conservation in the inelastic scattering event. These modes can be
accessed with e-beams in the vacuum far-field zone, similarly to the recently
developed far-field optics based on surface plasmon resonances.
