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BP: Fachverband Biologische Physik

BP 26: Photobiophysics

BP 26.1: Vortrag

Freitag, 27. März 2009, 11:00–11:15, ZEU 260

Photon statistics in the fluorescence from single light-harvesting complexes — •Gregor Hehl, Sandeep Pallikkuth, and Andreas Volkmer — 3rd Insitute of Physics, University of Stuttgart

The photosynthetic apparatus of purple bacteria contains pigment-protein complexes that are optimized for efficient energy transfer, such as the light-harvesting complex (LH2) with bacteriochlorophyll a (BChla) pigments arranged in ring-like structures. Strong electronic interaction among the BChla governs their excited state properties, which are theoretically described in terms of excitonic wave functions. In contrast to prior fluorescence excitation/emission single-molecule spectroscopy, here we report on the photon statistics in the fluorescence of individual LH2 complexes at room-temperature that provides information about photo-physical processes ranging from picoseconds to milliseconds. The fluorescence of individual LH2 complexes is investigated by means of their photon arrival times, and analyzed in terms of interphoton time distributions and second-order correlation functions. These measurements revealed photon antibunching at short times, indicating sub-Poissonian photon statistics and singlet-singlet annihilation, and an excitation power-dependent photon bunching effect at longer times.