Osnabrück 2002 – wissenschaftliches Programm
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MO: Molekülphysik
MO 11: Femtosekundenspektroskopie IV: molekulare Dynamik
MO 11.5: Vortrag
Mittwoch, 6. März 2002, 17:30–17:45, HS 15/E07
Quantum Control of Energy Flow in Photosynthesis — •Wendel Wohlleben1, Jennifer L. Herek2, Dirk Zeidler1, and Marcus Motzkus1 — 1Max-Planck-Institut für Quantenoptik, Garching, Germany — 2Chemical Physics, Lund University, Sweden
We present the first application of feedback optimized control to a biological system, namely the 125 kDa light harvesting antenna complex LH2 of Rhodopseudomonas acidophila, a photosynthetic bacteria. The system contains two types of pigment molecules, carotenoid (Car) and bacteriochlorophyll (BChl). Excitation in the Car from absorption of blue-green light is either lost in internal conversion (IC) or saved for photosynthesis by energy transfer (ET) to the BChl. We excite the Car with shaped fs pulses from a non-collinear optical parametric amplifier (525 nm, 30 fs) and monitor the ensuing energy flow by probing the transient absorption kinetics of Car and BChl. These provide feedback for an evolutionary algorithm in a learning loop that optimizes the excitation pulse shape, attaining a 37% change compared to the natural energy partitioning ratio. Additionally we study control fields that differ only in the carrier phase pattern across the pulse and offer evidence of molecular coherence being exploited by the control mechanism.