Few-femtosecond passage of conical intersections in the benzene cation

• Published in: Nature communications Vol. 8; no. 1; pp. 1018 - 7
• Main Authors: Galbraith, M. C. E., Scheit, S., Golubev, N. V., Reitsma, G., Zhavoronkov, N., Despré, V., Lépine, F., Kuleff, A. I., Vrakking, M. J. J., Kornilov, O., Köppel, H., Mikosch, J.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 18.10.2017; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/36/2796; 639/766/94; Benzene; Cations; Chemical Sciences; Engineering Sciences; Femtochemistry; Femtosecond pulses; Humanities and Social Sciences; Hydrocarbons; I.R. radiation; Infrared lasers; Internal conversion; Intersections; Molecular dynamics; multidisciplinary; Photochemical reactions; Photochemicals; Physics; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-017-01133-y

Observing the crucial first few femtoseconds of photochemical reactions requires tools typically not available in the femtochemistry toolkit. Such dynamics are now within reach with the instruments provided by attosecond science. Here, we apply experimental and theoretical methods to assess the ultrafast nonadiabatic vibronic processes in a prototypical complex system—the excited benzene cation. We use few-femtosecond duration extreme ultraviolet and visible/near-infrared laser pulses to prepare and probe excited cationic states and observe two relaxation timescales of 11 ± 3 fs and 110 ± 20 fs. These are interpreted in terms of population transfer via two sequential conical intersections. The experimental results are quantitatively compared with state-of-the-art multi-configuration time-dependent Hartree calculations showing convincing agreement in the timescales. By characterising one of the fastest internal conversion processes studied to date, we enter an extreme regime of ultrafast molecular dynamics, paving the way to tracking and controlling purely electronic dynamics in complex molecules. Attosecond science is beginning to provide the tools to study the previously unattainable crucial first few femtoseconds of photochemical reactions. Here, the authors investigate extremely rapid population transfer via conical intersections in the excited benzene cation, both by experiment and computation.