title: How Static Disorder Mimics Decoherence in Anisotropy Pump-Probe Experiments on Purple-Bacteria Light Harvesting Complexes.
abstract: Anisotropy pump-probe experiments have provided insights into the character of excitons formed in photosynthetic complexes. Rapid decay in the observed anisotropy is cited as evidence of the strength of coupling of the excitonic degrees of freedom to their environment. Here we show that ensemble averaging over realistic model Hamiltonians leads to a rapid decay of anisotropy to a value close to the observed asymptote, and at a rate comparable to observed decay rates, even in the absence of coupling to the environment. While coupling to the environment will clearly play a role in the dynamics of such systems, our calculations suggest that caution is needed in deducing the strength of this coupling from anisotropy experiments. We also set out to clarify the nature of the quantum states and processes involved in the dynamics of such systems and the associated terminology.
authors.affiliation: Centre for Computational Chemistry, School of Chemistry, University of Bristol , Bristol BS8 1TS, U.K.|School of Mathematics, University of Bristol , Bristol BS8 1TW, U.K.
authors.forename: Clement
authors.initials: C
authors.lastname: Stross
authors.affiliation: Centre for Computational Chemistry, School of Chemistry, University of Bristol , Bristol BS8 1TS, U.K.
authors.forename: Marc W
authors.initials: MW
authors.lastname: Van der Kamp
authors.affiliation: School of Chemistry, University of Bristol , Bristol BS8 1TS, U.K.
authors.forename: Thomas A A
authors.initials: TA
authors.lastname: Oliver
authors.affiliation: Centre for Computational Chemistry, School of Chemistry, University of Bristol , Bristol BS8 1TS, U.K.|Department of Chemistry, KU Leuven , Celestijnenlaan 200F, B-3001 Leuven, Belgium.
authors.forename: Jeremy N
authors.initials: JN
authors.lastname: Harvey
authors.affiliation: School of Mathematics, University of Bristol , Bristol BS8 1TW, U.K.
authors.forename: Noah
authors.initials: N
authors.lastname: Linden
authors.affiliation: Centre for Computational Chemistry, School of Chemistry, University of Bristol , Bristol BS8 1TS, U.K.
authors.forename: Frederick R
authors.initials: FR
authors.lastname: Manby
mesh_terms: D016880:Anisotropy; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000378:metabolism; D056004:Molecular Dynamics Simulation; D020560:Proteobacteria / Q000737:chemistry* / Q000378:metabolism; D011789:Quantum Theory
chemical_list: D045342:Light-Harvesting Protein Complexes