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MO: Fachverband Molekülphysik

MO 4a: Ultrafast Structural Dynamics II

MO 4a.1: Vortrag

Montag, 2. März 2026, 17:00–17:15, P 110

Ultrafast electron diffraction imaging of chemical substitution effects on nonadiabatic nuclear dynamics at conical intersections — •Sudhir Kumar¹, Joanne Woodhouse¹, Athira Mini Santhosh¹, Simone Stahl¹, Jin Cheng², Hui Jiang², Tianyu Wang², Dao Xiang², and Kasra Amini¹ — ¹Max-Born-Institut, Max-Born-Straße 2A, 12489 Berlin, Germany — ²Shanghai Jiao Tong University, 200240 Shanghai, China

We investigate nonadiabatic molecular dynamics in the α,β-unsaturated aldehyde family using ultrafast electron diffraction (UED) to simultaneously probe electronic and nuclear dynamics. We examine the effect of methyl substitution by comparing acrolein (2-propenal) and crotonaldehyde (2-butenal) following excitation to the short-lived S₂ (ππ^*) state at 200 nm. Population transfer proceeds through the S₂/S₁ minimum-energy conical intersection, leading to the S₁ minimum accompanied by torsional motion of the terminal methylene group. Subsequent relaxation occurs either via intersystem crossing to triplet-state dissociation according to Lee et al. [1], or through the S₁/S₀ conical intersection resulting in singlet-state dissociation, while we observe an approximately equal (50:50) branching ratio between singlet and triplet dissociation channels in acrolein.

[1] A. M. D. Lee et al., J. Phys. Chem. A 111, 11948 (2007).

Keywords: Coupled electronic-nuclear dynamics; ultrafast electron diffraction; femtochemistry; gas-phase photochemistry