Theoretical studies of molecular scale near-field electron dynamics

Near-field scanning microscopy and nonlinear spectroscopy on a molecular scale involve weakly interacting subsystems that dynamically exchange electrons and electromagnetic energy. The theoretical description of such processes requires unified approach to the electron-near-field dynamics. By considering electronic structure and dynamics of two distant clusters or atoms we show that adiabatic local spin-density approximation (ALSDA) fails to describe (even qualitatively) essential details of electron dynamics in weakly interacting systems. A recently developed functional addresses these ailments within a time-dependent setting. With this method we study the spectroscopy of a composite system, namely, two weakly coupled metallic clusters. The near-field (dipole-dipole) coupling and electron transfer display an interesting interplay, producing exponential sensitivity of emission yield to the intercomponent distance.