Surface-polariton excitation by charged particles on a plate

The excitation of surface polaritons when a charged particle passes through a plate is considered. A general expression is found for the spectral energy distribution of the polaritons of two possible branches without any restrictions placed on the parameters of the problem. Particular attention is given to the case of slow surface polaritons, when time lag can be neglected. It is shown that the polariton energy oscillates as a function of plate thickness and excitation-charge velocity.