REAL-SPACE COUPLED-OSCILLATOR APPROACH TO THE RADIATIVE DECAY OF CONJUGATED POLYMERS

The optical response of conjugated polymers is calculated using a one- dimensional tight-binding model with Coulomb interactions, and adoptin g the multipolar form for the electromagnetic field Hamiltonian. By fo rmulating the problem using the reduced single-electron density matrix and its evolution in Liouville space, we obtain a real-space descript ion for the elementary electronic excitations. A unified expression fo r the linear response including radiative decay, which is valid for ar bitrary chain size compared with the optical wavelength, is described. For small sizes it shows exciton confinement effects on the radiative decay and for larger sizes it fully incorporates polariton effects.