Freiburg 2024 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 23: Poster: Chirality
MO 23.6: Poster
Donnerstag, 14. März 2024, 17:00–19:00, Tent C
Time-Resolved Circular Dichroism Spectroscopy with Ultrafast Broadband Circularly Polarized Laser Pulses — •Karina Heilmeier1, Emely Freytag2, Christina Kaufmann2, Frank Würthner2, Christoph Lambert2, and Tobias Brixner1 — 1Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany — 2Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
Chiral exciton states that have a small dipole strength have only weak contributions in linear absorption spectroscopy. However, such states can be well resolved with circular dichroism spectroscopy. Analogously, time-resolved circular dichroism (TRCD) spectroscopy may give information on the ultrafast dynamics of these exciton states which cannot be resolved with non-chiral transient absorption spectroscopy.[1]
Here, we report a TRCD setup based on the pump–probe approach employing ultrafast broadband white-light probe pulses with left- and right-handed circular polarization. The circular polarization is induced by a polarization grating. In TRCD one measures the difference in absorption of left- and right-circularly polarized light of the excited and non-excited states. To investigate the dynamics of chiral excitons, measurements were carried out on a chiral squaraine dimer and a chiral perylene bisimide dimer, both exhibiting excitonic coupling.
[1] L. Ress, P. Malý, J. B. Landgraf, D. Lindorfer, M. Hofer, J. Selby, C. Lambert, T. Renger, T. Brixner, Chem. Sci. 14, 9328 (2023).
Keywords: Circular Dichroism; Ultrafast Spectroscopy; Chirality; Excitonic Coupling