Over the last several decades, the light-harvesting protein complexes of purple bacteria have been among the most popular model systems for energy transport in excitonic systems in the weak and intermediate intermolecular coupling regime. Despite this extensive body of scientific work, significant questions regarding the excitonic states and the photo-induced dynamics remain. Here, we address the low-temperature electronic structure and excitation dynamics in the light-harvesting complex 2 of Rhodopseudomonas acidophila by two-dimensional electronic spectroscopy. We find that, although at cryogenic temperature energy relaxation is very rapid, exciton mobility is limited over a significant range of excitation energies. This points to the presence of a sub-200 fs, spatially local energy-relaxation mechanism and suggests that local trapping might contribute substantially more in cryogenic experiments than under physiological conditions where the thermal energy is comparable to or larger than the static disorder.
Intraband dynamics and exciton trapping in the LH2 complex of Rhodopseudomonas acidophila
Note: This paper is part of the JCP Special Topic on Excitons: Energetics and Spatio-Temporal Dynamics.
Erling Thyrhaug, Marco Schröter, Eglė Bukartė, Oliver Kühn, Richard Cogdell, Jürgen Hauer, Donatas Zigmantas; Intraband dynamics and exciton trapping in the LH2 complex of Rhodopseudomonas acidophila. J. Chem. Phys. 28 January 2021; 154 (4): 045102. https://doi.org/10.1063/5.0033802
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