Exciton States and Optical Spectra in Linear Molecular Crystals

Abstract

Configuration interaction of many Frenkel exciton bands and charge-transfer states is carried out exactly. Based on the exact solution of the problem, the optical spectra is discussed. If the monomolecular optical transition is allowed, the intensities of exact exciton states are borrowed from the Frenkel excitons. Within the borrowed intensity approximation, resonance peaks and antiresonance dips in the continuum band are expected to appear depending on the magnitude of parameters. Although locations of resonances are independent of the orientation of the light polarization vector, positions and numbers of antiresonances do depend on it. Total number of antiresonances is at most one less than the number of Frenkel exciton bands. In the absence of resonance the continuum intensity depends very strongly on the nearest-neighbor charge pair interaction energy with larger intensity for smaller interaction energy. For the discrete spectra, the intensity is mainly distributed to the number of states equal to or one more than the number of Frenkel exciton bands. The relative intensities of these lines depend on the orientation of the light polarization vector. The intensity and position of the extra line varies with the nearest-neighbor charge pair interaction energy.