Decoherence in Weakly Coupled Excitonic Complexes

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 115; no. 16; pp. 3845 - 3858
• Main Authors: Mančal, Tomáš, Balevičius, Vytautas, Valkunas, Leonas
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 28.04.2011
• Subjects: Fluorescence Resonance Energy Transfer; Models, Chemical; Photoelectron Spectroscopy; Quantum Theory
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp108247a

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.