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MO: Fachverband Molekülphysik
MO 1: Biomoleküle
MO 1.4: Talk
Monday, March 10, 2008, 15:00–15:15, 3F
Investigation of Optically "Dark" Excited States of Carotenoids by Femtosecond Two-Photon Excitation Spectroscopy — •Alexander Betke1, Bernd Voigt1, Heiko Lokstein2, and Ralf Menzel1 — 1Institut für Physik/Photonik, Universität Potsdam, Am Neuen Palais 10, D-14415 Potsdam, Germany — 2Institut für Biochemie und Biologie, Universität Potsdam, Karl- Liebknecht-Str. 24-25, D-14476 Potsdam-Golm, Germany
Carotenoids are essential components of pigment-protein-complexes in photosynthetic organisms: they are important for structural stability, serve as accessory light-harvesting pigments and protect the photosynthetic apparatus from photo-oxidative damage. The carotenoid lowest excited singlet state S1 (21Ag−) is assumed to be relevant for the latter two functions. For a study of the underlying mechanisms a proper knowledge of its energetic position would be necessary. However, single photon transitions between the carotenoid ground state S0 (11Ag−) and this state are symmetry-forbidden and thus, its investigation by conventional spectroscopy is hampered. On the other hand the S0-S1-transition is two-photon allowed, which makes two-photon absorption a suiteable approach for an investigation of the carotenoid S1 energies. We present near-infrared femtosecond laser two-photon excitation spectra of light-harvesting antenna-complexes with different carotenoid complements and discuss implications for excitation energy transfer and photoprotective mechanisms.
This research is supported by the DFG (SFB 429, TP A2).