Kinematical interaction of optical excitations and consequences

Abstract

The effects of the kinematical interaction of optical excitations were analyzed. The energies of the additional, kinematical excitations, arising due to the three-particle boson processes, were found and compared to the energies of the normal excitonic states. It was also shown that the sharp absorption peak, appearing in the low frequence domain of the optical spectra, arises due to the exciton-exciton interaction. The broadening of the kinematical levels was estimated and it was concluded that the anomally high broadening of optical levels cannot be attributed to the kinematical interaction of excitons. In the frequency range close to the resonance, Urbach's rule was reproduced. The theoretical values of Urbach's coefficient are in a good agreement with the experimental data. © 1988.