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MO: Fachverband Molekülphysik
MO 1: Ultrafast Structural Dynamics
MO 1.6: Vortrag
Montag, 2. März 2026, 13:00–13:15, P 105
Antisymmetric vibrations in the excited state dynamics of quadrupolar dyes — Somayeh Souri1, Katrin Winte1, Daniel Lünemann1, Daniel Timmer1, Elena Mena-Osteritz2, Sergei Tretiak3, Christoph Lienau1, and •Antonietta De Sio1 — 1Universität Oldenburg — 2Universität Ulm — 3Los Alamos National Laboratory
Non-equilibrium dynamics following photoexcitation in molecular materials arise from a complex interplay of electronic and vibrational motion, with antisymmetric vibrations playing a key role in ultrafast nonadiabatic dynamics, such as at conical intersections. Their direct spectroscopic identification is, however, challenging, since these modes are often Raman inactive and only weakly affect optical transitions. Here, we show experimental signatures of vibronic coupling to antisymmetric modes in the ultrafast symmetry-breaking dynamics of a quasi-quadrupolar dye[1,2] using two-dimensional electronic spectroscopy (2DES). The sub-50-fs 2DES maps reveal an asymmetric peak pattern with characteristic low-energy cross-peaks. We show that these peaks arise from stimulated emission from a double-minimum excited state potential energy surface induced by vibronic coupling to a ~1430 cm-1 antisymmetric mode[2]. Phenomenological essential state model simulations support the results. Our findings show that 2DES with sub-cycle vibrational resolution is a powerful method for identifying antisymmetric modes in the excited state dynamics prior to intramolecular vibrational relaxation and solvation. [1] Winte et al, Nature Chemistry 17, 1742 (2025); [2] Souri et al, submitted (2025)