Propagation of electronic excitation on a polymer chain

Abstract

In this thesis, we study a model system of a linear polymer chain in terms of time-dependent Schrodinger equation in the tight-binding representation. We have shown that the continuous limit of a discrete model can be formulated in terms of Feynman's path integrals. We introduce randomness to the system and study in the case where the electronic excitation energy is distributed Gaussian randomly. The Feynman propagator leads to the density of states which is important to evaluate the spectral density function. We also obtain the spectral density function of electronic excitation of a polymer chain consisting of identical monomers in 3D system under the influence of lattice vibrations, the nearest neighbor intermolecular coupling and absence of internal vibrations. In the low-energy range, we obtain the spectral density function as the asymmetric line shape. The width of the electronic excitation line shape is directly proportional to the fluctuationsof the system. If the width is wide (narrow) then there is high (low) fluctuation.