Anomalous optical selection rule of an organic molecule controlled by extremely localized light field

Abstract

We have theoretically demonstrated the drastic enhancement of light-induced electric polarization in molecular nondipole type dark states. Its magnitude can exceed that of bright states, even in a nanoscale molecule, due to the spatial correlation between the wave function of the excited states and the localized light field. Moreover, it was clarified that the direct observation of such an anomalous enhancement of dark states in a metal nanogap is possible through near field spectroscopy under one-photon excitation. The results obtained will open the way to single molecule detection methods to reveal the molecular level scheme including parity-forbidden states. © 2011 American Institute of Physics.