Heidelberg 2015 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 18: Biomolecules
MO 18.4: Vortrag
Donnerstag, 26. März 2015, 12:00–12:15, PH/SR106
Ultrafast coupling dynamics between the excited states of open chain carotenoids observed by fs time-resolved nonlinear vibrational spectroscopy — •Takeshi Miki1, Richard J. Cogdell2, Tiago Buckup1, and Marcus Motzkus1 — 1Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany — 2Institute of Biomedicine & Life Science, University of Glasgow, G12 8QQ Glasgow, Lanark, Scotland
The ultrafast femtochemistry of carotenoids is governed by the interaction between electronic excited states. Electronic dark states of carotenoids and their interaction with optically active S2 state have been suggested to play a major role in the ultrafast deactivation of carotenoids and its properties. Here, we investigate this interaction between such dark and bright electronic excited states of open chain carotenoids, particularly its dependence on the number of conjugated double bonds (N). We focus on the ultrafast wave packet motion on the modified potential surface by the interaction between bright and dark electronic states. Pump-degenerate four-wave mixing (pump-DFWM) is applied to a series of carotenoids with different number of conjugated double bonds N = 9, 10, 11 and 13. Our results indicate that short carotenoids display strongly distorted potentials when compared to longer carotenoids. The magnitude of this anharmonicity can be explained by the efficient coupling between S2 and a dark Sx state (in this case a Bu type), which stabilizes the higher energy levels of the C-C and C=C vibrational modes at early delay times (T < 50 fs).