SAMOP 2023 – scientific programme
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MO: Fachverband Molekülphysik
MO 2: Photochemistry
MO 2.5: Talk
Monday, March 6, 2023, 12:00–12:15, F142
Multireference Chlorophyll Nuclear and Electron Q-Band Dynamics: a Theoretical XAS Study — •Lena Bäuml, Sebastian Reiter, Florian Rott, Bastian Michels, and Regina de Vivie-Riedle — Department of Chemistry, LMU Munich, Germany
Chlorophylls play a vital role during photosynthetic light-harvesting. Here, the nonradiative relaxation of high-energy excited states to the lowest excited state is of central importance.
We simulate the ultrafast relaxation process in the Q-bands of chlorophyll in a representative 2D space using grid-based wave packet quantum dynamics. The excited state energies and potential energy surfaces are computed at the XMS-CASPT2 level of theory to capture the multi-reference character of chlorophyll excitations. We propose a possibility to observe the wave packet dynamics, as well as the strong coupling between the Qx and Qy state via magnesium K-edge X-ray absorption spectra. Following the RASPT2 procedure outlined by Rott et al.[1] our results show from a fully quantum mechanical point of view how the Qx and Qy band are strongly coupled by internal vibrations,[2] in contrast to the Gouterman model. Thus the absorption intensity should be spread over the whole Q-band, influencing charge and energy transfer in photosynthetic light-harvesting complexes, such as photosystem 1.
[1] F. Rott et al., Struct. Dyn., 8, 034104 (2021).
[2] L. Bäuml et al., Phys. Chem. Chem. Phys. 24, 27212 (2022).