Density-operator description of excitons in molecular aggregates. IV. Optical spectra and excitonic motion in two-dimensional finite chains

Abstract

Our previous work, on calculations of excitonic absorption line shapes and motion in one-dimensional molecular chains, is extended to double molecular finite chains involving two-dimensional antisotropic intermolecular couplings of arbitrary magnitudes. Calculations of line shapes of double molecular chains, of various geometries and sizes, are presented in terms of the interchain coupling modifying the structure of the single chain. The exciton motion is discussed for the coherent and incoherent cases, in terms of the size (edge effects) and of the interchain motion which may modulate or dump the intrachain motion. In the limit of large sizes our equations are shown to meet the well-known results derived directly for infinite systems. Furthermore, the present work is presented as a prerequisite for calculations for a finite crystal of layered structure where the intermolecular couplings are two dimensional.