A single charge confined on the axis of a nanocylinder, carrying a charge of opposite sign, and two equal free classical charges on a conducting thin nanoring are two systems which can oscillate with frequencies in the THz domain. The potential energy obtained for the latter case can be generalized to n equal charges (n > 2). It can be shown that the n charges occupy positions on the ring corresponding to the n roots of unity at equilibrium.
charge oscillations; THz domain; nanoscopic system
