Mainz 2017 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 11: Molecular Nanostructures and Solids
MO 11.3: Vortrag
Mittwoch, 8. März 2017, 15:00–15:15, N 25
Coherent Two-Dimensional Spectroscopy of Exciton-Exciton Interactions — •Jakub Dostál1, Federico Koch1, Stefanie Herbst2, Pawaret Leowanawat2, Frank Würthner2, and Tobias Brixner1 — 1Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg — 2Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg
Many important light-induced processes in molecular systems rely on multi-photon excitation of the sample. The studying of such processes requires reliable discrimination between the multi- and single-exciton signals, which might become a challenging task for many common methods of time-resolved spectroscopy.
Here we show that the fifth-order three-pulse optical signal characterized by the −2k1 + 2k2 + k3 phase-matching relation is specific to bi-exciton processes, i.e., it emerges only if the presence of one exciton in the sample influences the behavior of another one. Further we show how this signal can be used for construction of two-dimensional spectrum of exciton-exciton interactions (EEI 2D) and derive some of its properties. The entire concept is experimentally demonstrated on the exciton annihilation process present in perylene bisimide J-aggregates. We observe the rise of the EEI signal as pairs of initially independent excitons located along one of the aggregate strains are brought together by the random diffusive motion and annihilate.
The proposed EEI 2D method can provide detailed understanding of versatile bi-exciton processes in molecular systems.