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O: Fachverband Oberflächenphysik
O 88: Focus Session: Ultrafast Processes in Organic Semiconductors and Perovskites II (joint session O/CPP)
O 88.5: Talk
Thursday, March 21, 2024, 16:15–16:30, MA 004
Excited state symmetry breaking and solvation in quadrupolar dyes — •Katrin Winte1, Somayeh Souri1, Daniel Lünemann1, Fulu Zheng2, Mohamed Madjet2, Teresa Kraus3, Elena Mena-Osteritz3, Peter Bäuerle3, Sergei Tretiak4, Antonietta De Sio1, and Christoph Lienau1 — 1Oldenburg University, Germany — 2Bremen University, Germany — 3Ulm University, Germany — 4Los Alamos National Laboratory, USA
Quadrupolar acceptor-donor-acceptor (A-D-A) dyes represent a versatile and chemically tunable class of prototypical molecular systems for exploring photo-induced charge transfer processes. Their optoelectronic properties are governed by an interplay between electronic tunneling between two arms and vibronic coupling to high frequency modes in each arm. In polar solvents, optical excitation results in a pronounced solvatochromism thought to arise from a light-induced charge localization inside the molecule, induced by an interplay between intramolecular charge separation and solvation[1]. So far, both processes could not be distinguished experimentally. Here, we report the first observation of the vibronic-coupling induced nonadiabatic charge separation in A-D-As. By comparing pump-probe and 2DES spectra recorded with 10fs time resolution in polar and nonpolar solvents, we demonstrate coherent vibrational wavepacket motion during the first 100fs that is largely unaffected by solvation. Our results give evidence for a vibronic-coupling induced double-minimum potential energy surface inducing spontaneous symmetry breaking and charge separation after photoexcitation. [1] E. Vauthey, J. Phys. Chem. Lett. 13,2064 (2022).
Keywords: Quadrupolar dyes; Nonadiabatic coupling; Solvatochromism; Excited state symmetry breaking; Ultrafast spectroscopy