Non-adiabatic electronic and vibrational ring-opening dynamics resolved with attosecond core-level spectroscopy K.M. Ziems 1,† , S. Severino 2,† , M. Reduzzi 2 , A. Summers 2 , H.-W. Sun 2 , Y.-H. Chien 2 , S. Gräfe 1,3,4 , J. Biegert 2,5,* 1 Friedrich-Schiller-University Jena, Germany, 2 The Barcelona Institute of Science and Technology, Spain, 3 Fraunhofer Institute for Applied Optics and Precision Engineering, Germany, 4 Institute of Applied Physics and Abbe Center of Photonics, Friedrich-Schiller-Universität Jena, Germany, 5 ICREA, Spain † These authors contributed equally Non-adiabatic dynamics and conical intersections play a central role in the chemistry of most polyatomic molecules, ranging from isomerization to heterocyclic ring opening and avoided photo-damage of DNA. Studying the underpinning correlated dynamics of electronic and nuclear wave packets is a major challenge in real-time and, many times involves optically dark transient states. For a complete investigation of these dynamics, a spectroscopic tool capable of disentangling the electron and nuclear degrees of freedom with sub-nanometer spatial, and sub-fs temporal resolution is needed. Combining a strong-field pump with attosecond soft x-ray (SXR) pulses [1,2], we show that time-resolved attosecond core-level spectroscopy (tr-AttoXAFS) is capable of meeting these requirements. We present a joint experimental and theoretical study of the pathway dynamics of neutral furan across its conical intersections and dark states.[3] Upon strong-field excitation, we identify electronic coherence between excited states mediated by conical intersections. This manifests as Carbon-site sensitive quantum beating in the absorption signal. We detect electronic-nuclear correlations as dephasing of electronic coherence due to nuclear motion and identify the ring-opened isomer as the dominant product. These results demonstrate the efficacy of attosecond core level spectroscopy as a potent method to investigate the real-time dynamics of photochemical reaction pathways in complex molecular systems.
Fig. 1: Differential absorption (ΔA) as function of the pump-probe delay and the probe photon energy. Marked in orange (magenta) is the relevant XAFS feature of the ππ* (πσ*) state; (b): Short Time Fourier Transform (STFT) of the background- subtracted signal at 287eV with the quantum beating frequency of 63±9 THz (orange) followed by a vibrational frequency of 36±9 THz (magenta) showing dephasing at the conical intersection (CI). References 1. S. M. Teichmann et al., “0.5-keV Soft X-Ray Attosecond Continua”, Nat. Commun. 7, 11493 (2016). 2. B. Buades et al., “Attosecond dispersive soft X-ray absorption fine structure spectroscopy in graphite”, Optica 5, 502-506 (2018) 3. Severino et al., “Non-Adiabatic Electronic and Vibrational Ring-Opening Dynamics resolved with Attosecond Core-Level Spectroscopy”, arXiv:2209.04330
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