Photoexcitation spectra of polyacetylene and polyaniline: a three-dimensional model for conducting polymers

Summary form only given. We propose a concept of a localized charge-transfer exciton, based on the fact that the real samples of conducting polymer are composed of neutral finite-length. fragments of the polymer chains [1]. The states of such exciton involve the excited state of one fragment and the states where one of its electons is transferred to neighbor fragments. These states appear when one photon with energy h/spl nu/ /spl cong/ /splk utri/E /spl cong/ 2 eV is absorbed, where /spl utri/E is the energy of the intense maximum in the absorption spectrum. The following energy relation provides a means for such a transfer: I - A - P - G /spl cong/ /spl utri/E, where I /spl cong/ 6 eV and A /spl cong/ 1 eV is the ionization potential and the electron affinity of neutral fragment, (-G) /spl les/ 1 eV is the Coulomb interaction energy of two charged fragments, and P /spl cong/ 3 eV is the energy of electronic polarization of polymer fragments in the Co ulomb field of two charged fragments. The photoexcitation spectra, which are nothing but the absorption spectra owing to transi tions between the states of the exciton, are simulated numerically for polyacetylene and polyaniline in accord with experiment.