title: Decoherence in weakly coupled excitonic complexes.
abstract: Equations of motion for weakly coupled excitonic complexes are derived. The description allows one to treat the system in the basis of electronic states localized on individual chromophores while at the same time accounting for experimentally observable delocalization effects in optical spectra. The equations are shown to be related to the well-known Förster type energy-transfer rate equations, but unlike Förster equations, they provide a description of the decoherence processes leading to suppression of the resonance coupling by bath fluctuations. Linear absorption and two-dimensional photon echo correlation spectra are calculated for simple model systems in the homogeneous limit, demonstrating a distinct delocalization effect and reduction of the resonance coupling due to interaction with the bath.
authors.affiliation: Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 5, CZ-121 16 Prague 2, Czech Republic. tomas.mancal@mff.cuni.cz
authors.forename: Tomáš
authors.initials: T
authors.lastname: Mančal
authors.forename: Vytautas
authors.initials: V
authors.lastname: Balevičius
authors.forename: Leonas
authors.initials: L
authors.lastname: Valkunas
mesh_terms: D031541:Fluorescence Resonance Energy Transfer; D008956:Models, Chemical; D056951:Photoelectron Spectroscopy; D011789:Quantum Theory