Regensburg 2000 – scientific programme

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SYBP: Biologie und Physik

SYBP 3: POSTER

SYBP 3.12: Poster

Thursday, March 30, 2000, 15:00–18:00, D

Excited-state photoemission spectroscopy of carotenoids — •C. Spitz — Max-Born-Institut , Max-Born-Str. 2A, D-12489 Berlin

The excited-state properties of the carotenoids are of particular importance for the understanding of the elementary processes which involve these molecules in photosynthetic systems. Here, we present well-resolved photoemission spectra from ß-carotene deposited by evaporation on a gold single-crystal surface in ultrahigh vacuum. From these data the HOMO and HOMO-1 energy levels can be directly derived. Experiments on the determination of the usually unoccupied S1 energy level of ß-carotene by two-color two-photon photoemission (2C-2PPE) using time-correlated laser and synchrotron pulses are currently performed. In this experiment the S1 state is populated by efficient S2–>S1 internal conversion following the excitation of the S2 state by a 200 fs laser pulse (SHG from a 80 MHz Ti:sapphire laser @ 410 nm). The synchrotron probe pulse is provided from the MBI User Facility at BESSY II. In addition, the S1 energy of ß-carotene is measured independently by inner-shell x-ray absorption using a x-ray laser plasma source.