Berlin 2014 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 6: Femtosecond Spectroscopy 1
MO 6.6: Vortrag
Dienstag, 18. März 2014, 12:00–12:15, BEBEL HS213
S2 to S1 Relaxation Dynamics in Perylene Bisimide Aggregates and Monomers — •Steffen Wolter1, Franziska Fennel1, Marco Schröter1, Frank Würthner2, Oliver Kühn1, and Stefan Lochbrunner1 — 1Institut für Physik, Universität Rostock, Universitätsplatz 3, 18055 Rostock — 2Institut für Organische Chemie und Center for Nanosystem Chemistry, Universität Würzburg, Am Hubland, 97074 Würzburg
In this contribution, the relaxation dynamics from the electronic S2 state to the S1 state of monomeric and aggregated perylene bisimide dyes are investigated by femtosecond pump-probe spectroscopy. The considered perylene bisimides are known for forming long J-aggregate chains at ambient conditions in which exciton migration and annihilation can occur. During the annihilation process, a transient population and fast relaxation of highly excited states is assumed. Therefore, the relaxation pathways of these highly excited states have to be investigated to understand the annihilation process itself.
To this end, ultrafast transient absorption measurements with excitation of the S2 and the S1 state are performed and compared to each other. After optical population of the S2 state a delayed onset of the stimulated emission from the S1 state is observed for the aggregate as well as for the monomer. This effect is induced by the S2 to S1 decay, which happens on an ultrafast time scale of less than 500 fs. The impact of aggregation on the S2 to S1 relaxation is discussed and the results are compared to theoretical predictions [1].
[1] Schröter M., Kühn O. J. Phys. Chem. A 117, 7580 (2013)