Photoinduced isomerization reactions lie at the heart of many chemical processes in nature. The mechanisms of such reactions are determined by a delicate interplay of coupled electronic and nuclear dynamics occurring on the femtosecond scale, followed by the slower redistribution of energy into different vibrational degrees of freedom. Here we apply time-resolved photoelectron spectroscopy with a seeded extreme ultraviolet free-electron laser to trace the ultrafast ring opening of gas-phase thiophenone molecules following ultraviolet photoexcitation. When combined with ab initio electronic structure and molecular dynamics calculations of the excited- and ground-state molecules, the results provide insights into both the electronic and nuclear dynamics of this fundamental class of reactions. The initial ring opening and non-adiabatic coupling to the electronic ground state are shown to be driven by ballistic S–C bond extension and to be complete within 350 fs. Theory and experiment also enable visualization of the rich ground-state dynamics that involve the formation of, and interconversion between, ring-opened isomers and the cyclic structure, as well as fragmentation over much longer timescales.
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Data generated or analysed during this study are included in this Article (and its Supplementary Information). Source data are provided with this paper.
The analysis codes used to generate the data presented in this study are available from the corresponding authors upon reasonable request. Source data are provided with this paper.
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S.P., J.T. and D.R. were supported by the National Science Foundation (NSF) grant PHYS-1753324. S.P. was also partially supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, US Department of Energy (DOE) under grant no. DE-FG02-86ER13491. Travel to FERMI for S.P., D.M.P.H., R.M., J.T. and D.R. was supported by LaserLab Europe. This work made use of the facilities of the Hamilton HPC Service of Durham University. M.N.R.A., C.S.H. and R.A.I. acknowledge the Engineering and Physical Sciences Research Council (EPSRC) for funding (EP/L005913/1), while L.M.I. acknowledges the EPSRC for a doctoral studentship (EP/R513039/1). C.S.H. also acknowledges funding from the Australian Research Council (ARC, DE200100549). M.N.R.A. thanks W.-H. Fang (Beijing Normal University) for permission to share data28 prior to its publication. B.F.E.C. acknowledges funding from the European Union Horizon 2020 research and innovation programme under grant agreement no. 803718 (SINDAM). D.M.P.H. was supported by the Science and Technology Facilities Council, UK. R.F. and R.J.S. acknowledge financial support from the Swedish Research Council, the Knut and Alice Wallenberg Foundation, Sweden, and the Faculty of Natural Science of the University of Gothenburg. We thank the technical and scientific teams at FERMI for their hospitality and their support during the beamtime. We also acknowledge helpful discussions with A. Rudenko during the preparation of the beamtime proposal and during the data interpretation and with S. Bhattacharyya during the data analysis and interpretation.
The authors declare no competing interests.
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Pathak, S., Ibele, L.M., Boll, R. et al. Tracking the ultraviolet-induced photochemistry of thiophenone during and after ultrafast ring opening. Nat. Chem. 12, 795–800 (2020). https://doi.org/10.1038/s41557-020-0507-3
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