Exciton-Phonon Bound State and the Vibronic Spectra of Solids

Abstract

The final-state interaction between an optically excited LO phonon and an exciton is studied within the framework of a simple two-state model of the exciton. Criteria for the existence of a bound state (EPBS) of the exciton-phonon system are derived, and binding energies and oscillator strengths are computed for various values of the parameters which characterize the model. Our results are consistent with the optical data reported recently for a wide class of ionic crystals with shallow excitons.