Nazari, M.; Bösch, C. D.; Rondi, A.; Francés-Monerris, A.; Marazzi, M.; Lognon, E.; Gazzetto, M.; Langenegger, S.M.; Häner, R.; Feurer, T.; Monari, A.; Cannizzo, Andrea (2019). Ultrafast dynamics in polycyclic aromatic hydrocarbons: the key case of conical intersections at higher excited states and their role in the photophysics of phenanthrene monomer. Physical Chemistry Chemical Physics, 21(31), pp. 16981-16988. Royal Society of Chemistry 10.1039/C9CP03147B
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2019 PCCP Phenanthrene Conical Intersection.pdf - Published Version Available under License Creative Commons: Attribution-Noncommercial (CC-BY-NC). Download (2MB) | Preview |
In this study we reveal the detailed photocycle of a phenanthrene monomer. Phenanthrene serves as a popular building block for supramolecular systems and as an archetypal molecule to study the photochemistry of polycyclic aromatic hydrocarbons. By means of femtosecond time-resolved UV-vis transient absorption spectroscopy and molecular modeling, we found that the first bright transition involves the second excited singlet state, which relaxes toward the lowest excited singlet state with a biphasic internal conversion through a conical intersection region: a fast coherent branching followed by an exceptionally slow (∼ps) incoherent internal conversion. We succeeded to pinpoint the complete relaxation pathways and to extract the relevant parameters, e.g., the branching ratio at the conical intersection and internal conversion rates.
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