Charge Transfer and Electron-Molecular Vibration Coupling in Tetramerized Quasi-lD Semiconductors

Electron-molecular vibration coupling in tetramerized organic ion-radical semiconductors is considered. Eigenvalues and eigenfunctions of the molecular tetramer with two electrons are calculated in terms of extended Hubbard model parameters. The energy inequivalence of the monomer sites is introduced explicitly. The complex frequency dependent conductivity of the tetramerized compounds is found to produce a number of sharp maxima due to indirect excitation of the totally symmetric (ag) internal molecular modes of vibrations. These peaks are shown to have a fine structure if the charge density is not shared equally by the constituent molecules. The calculated reflectance is compared with the measured one for TEA (TCNQ)2 single crystals. [Russian Text Ignored].