Non‐linear optical susceptibilities of molecular crystals in the region of vibronie excitations. III. Non‐totally symmetric vibrations

Abstract

The quadratic optical susceptibility of molecular crystals is calculated in the frequency region of vibronic excitations consisting of an electronic exciton and a non-totally symmetric vibration. An one-dimensional model with nearest-neighbour interactions is used. Intermolecular and intramolecular exciton-phonon interactions are considered and the former is shown to play a dominant role in nonlinear optical spectra. The sign of the exciton effective mass is shown to affect the spectrum inside the two-particle exciton-phonon band but not the bound state resonance.