Bonn 2025 – wissenschaftliches Programm

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SYAD: Symposium SAMOP Dissertation Prize 2025

SYAD 1: SAMOP Dissertation Prize Symposium

SYAD 1.1: Hauptvortrag

Montag, 10. März 2025, 14:30–15:00, HS 1+2

A simple method to separate single- from multi-particle dynamics in time-resolved spectroscopy — •Julian Lüttig — University of Michigan, Ann Arbor, USA

The interpretation of time-resolved spectroscopy such as transient absorption (TA) relies on the isolation of a specific nonlinear order, typically the third order, of the sample response. Usually the excitation power is chosen low enough to suppress unwanted higher orders such as exciton–exciton annihilation. However, measurements at low excitation power often exhibit poor signal-to-noise ratio and the contamination by higher-order contributions cannot be quantified. In the opposite case of too high powers, higher-order signals connected to multi-particle dynamics are present and have to be considered in the analysis. We developed a technique using linear combinations of TA spectra at selective powers to extract uncontaminated nonlinear signal contributions. Thus, we access single-particle signals with high signal-to-noise ratio and obtain separate multi-particle dynamics [1,2]. Our technique can be easily implemented in any TA experiment and is applicable to any type of quantum system. We measured a broad variety of samples such as quantum dots, photosynthetic complexes, silicon nanocrystals, and polymers. The method provides direct access to the various terms of the perturbative expansion of light–matter interaction allowing one to systematically increase the number of interacting particles, infer their interaction energies and reconstruct their dynamics.
[1] P. Malý et al., Nature 2023, 616, 280.
[2] J. Lüttig et al., J. Phys. Chem. Lett. 2023, 14, 7556–7573.

Keywords: Time-resolved spectroscopy; Transient absorption; Multi-particle interaction; Exciton-exciton annihilation