Excitation of surface plasmons by electrons in a parabolic beam

A theory is presented for the excitation of surface plasmons by an electron beam following a non-touching path above a metal surface in Born approximation. The metal is assumed to possess only surface plasmon excitations. Configurations involving deflection of the electron beam in a parallel plate condensor, and by scattering from a field emission tip are envisaged. The relation between experimental conditions and the validity of the semiclassical approximation is discussed. The region of space above the surface in which scattering occurs is calculated, but the feasability of the experiment depends on electron optical factors which are outlined.