Bonn 2025 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 22: Ultrafast Dynamics III
MO 22.3: Vortrag
Donnerstag, 13. März 2025, 11:30–11:45, HS XVI
Isolating (multi-)exciton dynamics via fluorescence-detected pump–probe spectroscopy — •Stefan Mueller1, Ajay Jayachandran1, 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
Action-detected nonlinear spectroscopy has received increasing attention in the past years. While useful, it has recently been identified that action-based nonlinear spectra can be subject to undesired background stemming from incoherent mixing. This effect obscures single-exciton dynamics and is especially dramatic in systems with an increasing number of chromophores [1]. Moreover, inevitable pulse overlap causes artificial multiple-quantum coherences [2]. Both incoherent mixing and artificial multiple-quantum coherence reduce the meaningfulness of action-based spectra and exacerbate their interpretation. Here we introduce a technique that eliminates both undesired contributions. We demonstrate our approach using fluorescence-detected pump–probe spectroscopy (F-PP) on squaraine dimers and polymers. We extract fourth- and sixth-order F-PP spectra to isolate single- and bi-exciton dynamics, respectively, without spurious background. This works even in polymers which suffer to a particularly large degree from incoherent mixing due to the large number of involved chromophores.
[1] L. Bolzonello et al., J. Phys. Chem. Lett. 14, 11438 (2023).
[2] U. Bangert et al., Opt. Lett. 48, 538–541 (2023).
Keywords: Fluorescence-detected nonlinear spectroscopy; Phase cycling; Incoherent mixing; Annihilation; Exciton dynamics