Dynamical Theory of Electron-Phonon Bands

Abstract

Any stochastic theory for the optical band fails to describe a number of details found in realistic optical bands of impurity centers. For instance, stochastic theories are unable to explain why the optical band of a guest molecule has a rather complicated shape and, as a rule, consists of a zero-phonon line and a phonon side band. Nor can they explain why conjugate absorption and fluorescence bands whose zero-phonon lines are in resonance with each other can differ in shape. Real electron-phonon bands consist of an infinite set of electron-phonon transitions. From the point of view of the Anderson theory discussed above, the frequency of the optical transition in such a band jumps between an infinite number of spectral positions. The stochastic approach loses simplicity when applied to such a system. Therefore, electron-phonon optical bands and vibronic spectra of complex organic molecules with well-resolved phonon and vibrational structure can only be examined with the help of a dynamical theory.