Hannover 2003 – scientific programme
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MO: Molekülphysik
MO 9: Ultraschnelle Elektronendynamik
MO 9.6: Talk
Thursday, March 27, 2003, 15:15–15:30, B 302
Double pump-probe spectroscopy on deactivation of photoexcitation in carotenoids — •Tiago Buckup1, Wendel Wohleben1, Jennifer L. Herek2, Richard J. Cogdell3, and Marcus Motzkus1 — 1MPI für Quantenoptik, 85748 Garching — 2AMOLF, Amsterdam, The Netherlands — 3IBLS, University of Glasgow, UK
Here we apply the concept of double pump-probe spectroscopy to carotenoids with 11 conjugated double bonds in solution. By interrupting the relaxation from S2 to S1 with a second pump pulse (795nm), we deplete selectively the S1 channel but not the neighbouring excited state absorption. The classical three-level scheme describes the deactivation of the photoexcited S2 state with ultrafast internal conversion to the S1 state which in turn decays to the ground state S0 on the picosecond time scale, however our approach proves unambiguously the existence of an new independent deactivation channel via a fourth state S* in free carotenoids. Finally we apply an evolutionary target analysis to time-resolved transient absorption spectra, implementing a five-state model (S2 , S*, hotS1 , S1 , S0 ).