Energy transport and optical line shapes in dimers: Analytical description of the influence of colored noise

For a dimer, i.e., the simplest molecular aggregate, the influence of local vibrations on the transport of electronic excitation energy and on the optical absorption line shape is investigated. The vibrations give rise to site energy fluctuations which are described by a dichotomic stochastic process with colored noise. The model includes also the limits of static and infinitely fast fluctuations. The equations of motion for the density matrix of the system and for the correlation functions describing the optical line shape are calculated analytically. The coherence of transport properties, the time dependence of the memory function of the generalized master equation, optical line shapes, and the connection between them are discussed.