Freiburg 2024 – scientific programme
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MO: Fachverband Molekülphysik
MO 21: Ultrafast Dynamics II
MO 21.9: Talk
Thursday, March 14, 2024, 16:30–16:45, HS 3044
Following the Chlorophyll Coupled Dynamics with High-Level Multireference X-ray Absorption Spectra — •Lena Bäuml and Regina de Vivie-Riedle — Department of Chemistry, LMU Munich, Germany
The omnipresent natural pigment chlorophyll is crucial for photosynthetic light-harvesting. Its nonradiative relaxation from high-energy excited states to the ground state is still not fully understood.
In an already published study we could show that the Qx and Qy band are strongly coupled via internal vibrations by applying grid-based wavepacket quantum dynamics on representative XMS-CASPT2 potential energy surfaces[1]. We accounted for the coupled nuclear and electron dynamics using the NEMol ansatz developed in our group. Due to the strong coupling of the states we found the electronic coherence to be present during the entire simulation time. Transient X-ray absorption spectra (XAS) offer the possibility to resolve the ultrafast coupled dynamics experimentally. To predict the observed features we simulated XAS for the magnesium and nitrogen K-edge of chlorophyll a at the XMS-CASPT2 level of theory. We derived time-resolved XAS using a workflow to combine the static XAS with the coupled NEMol dynamics[2]. Explicitly accounting for the pump pulse we could follow the nuclear wavepacket dynamics as well as predict the influence of the electronic coherence on the XAS.
[1] L. Bäuml et al., Phys. Chem. Chem. Phys. 24, 27212 (2022).
[2] L. Bäuml et al., J. Phys. Chem. A, 127, 9787 (2023).
Keywords: simulated X-ray absorption spectra; coupled dynamics; chlorophyll a; XMS-CASPT2; photoinduced dynamics