Erlangen 2022 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 5: Femtosecond Spectroscopy I
MO 5.2: Vortrag
Dienstag, 15. März 2022, 11:00–11:15, MO-H6
Time-Resolved Circular Dichroism Spectroscopy of Exciton Relaxations in a Squaraine Polymer — •Lea Ress1, Joshua Selby2, Pavel Malý1,3, Jann B. Landgraf1, Dominik Lindorfer4, Christoph Lambert2, Thomas Renger4, 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 — 3Faculty of Mathematics and Physics, Charles University, Prague, Ke Karlovu 5, 121 16 Praha 2, Czech Republic — 4Institute for Theoretical Physics, Johannes Kepler University, Linz, Altenbergstrasse 69, 4040 Linz, Austria
We present a new design of a setup for simultaneous time-resolved circular dichroism (TRCD) and transient absorption (TA) spectroscopy with fs temporal resolution. We use a pump–probe approach by exciting the sample with a linearly polarized pump pulse and detecting the difference in absorption of left- and right-circularly polarized probe pulses. The key optical element is a polarization grating, out of which the positive (negative) first order of the diffracted light is left- (right-)circularly polarized. We demonstrate the power of this method on a chiral squaraine polymer, which shows ultrafast relaxations of chiral excitons. According to our calculations that are based on a Frenkel exciton Hamiltonian with quantum chemically parameterized excitonic couplings, using the helix model described in [1], exciton relaxation can be much better resolved with TRCD than with TA.
[1] A. Turkin, et al., Chem. Eur. J. 27, 8380-8389 (2021)