title: Direct visualization of exciton reequilibration in the LH1 and LH2 complexes of Rhodobacter sphaeroides by multipulse spectroscopy.
abstract: The dynamics of the excited states of the light-harvesting complexes LH1 and LH2 of Rhodobacter sphaeroides are governed, mainly, by the excitonic nature of these ring-systems. In a pump-dump-probe experiment, the first pulse promotes LH1 or LH2 to its excited state and the second pulse dumps a portion of the excited state. By selective dumping, we can disentangle the dynamics normally hidden in the excited-state manifold. We find that by using this multiple-excitation technique we can visualize a 400-fs reequilibration reflecting relaxation between the two lowest exciton states that cannot be directly explored by conventional pump-probe. An oscillatory feature is observed within the exciton reequilibration, which is attributed to a coherent motion of a vibrational wavepacket with a period of ∼150 fs. Our disordered exciton model allows a quantitative interpretation of the observed reequilibration processes occurring in these antennas.
authors.affiliation: Faculty of Sciences, Free University of Amsterdam, de Boelelaan, Amsterdam, The Netherlands. tacohenstuart@gmail.com
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Cohen Stuart
authors.forename: Mikas
authors.initials: M
authors.lastname: Vengris
authors.forename: Vladimir I
authors.initials: VI
authors.lastname: Novoderezhkin
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Cogdell
authors.forename: C Neil
authors.initials: CN
authors.lastname: Hunter
authors.forename: Rienk
authors.initials: R
authors.lastname: van Grondelle
mesh_terms: D007700:Kinetics; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D011487:Protein Conformation; D012242:Rhodobacter sphaeroides / Q000378:metabolism*; D013057:Spectrum Analysis / Q000379:methods*; D013816:Thermodynamics
chemical_list: D045342:Light-Harvesting Protein Complexes