Attosecond delays in X-ray molecular ionization

• Published in: Nature (London) Vol. 632; no. 8026; pp. 762 - 767J
• Main Authors: Driver, Taran, Mountney, Miles, Wang, Jun, Ortmann, Lisa, Al-Haddad, Andre, Berrah, Nora, Bostedt, Christoph, Champenois, Elio G, DiMauro, Louis F, Duris, Joseph, Garratt, Douglas, Glownia, James M, Guo, Zhaoheng, Haxton, Daniel, Isele, Erik, Ivanov, Igor, Ji, Jiabao, Kamalov, Andrei, Li, Siqi, Lin, Ming-Fu, Marangos, Jon P, Obaid, Razib, O'Neal, Jordan T, Rosenberger, Philipp, Shivaram, Niranjan H, Wang, Anna L, Walter, Peter, Wolf, Thomas J A, Wörner, Hans Jakob, Zhang, Zhen, Bucksbaum, Philip H, Kling, Matthias F, Landsman, Alexandra S, Lucchese, Robert R, Emmanouilidou, Agapi, Marinelli, Agostino, Cryan, James P
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 22.08.2024
• Subjects: Approximation; Electrons; Energy; Free electron lasers; Ionization; Lasers; Light effects; Nitric oxide; Nitrogen; Oxygen - chemistry; Photoelectric effect; Photoelectric emission; Photoelectricity; Photoelectron Spectroscopy - methods; Photoelectrons; Photoionization; Photon absorption; Photons; Resonance scattering; Soft x rays; Time Factors; Ultraviolet absorption; X-Rays
• ISSN: 0028-0836; 1476-4687; 1476-4687
• DOI: 10.1038/s41586-024-07771-9

The photoelectric effect is not truly instantaneous but exhibits attosecond delays that can reveal complex molecular dynamics . Sub-femtosecond-duration light pulses provide the requisite tools to resolve the dynamics of photoionization . Accordingly, the past decade has produced a large volume of work on photoionization delays following single-photon absorption of an extreme ultraviolet photon. However, the measurement of time-resolved core-level photoionization remained out of reach. The required X-ray photon energies needed for core-level photoionization were not available with attosecond tabletop sources. Here we report measurements of the X-ray photoemission delay of core-level electrons, with unexpectedly large delays, ranging up to 700 as in NO near the oxygen K-shell threshold. These measurements exploit attosecond soft X-ray pulses from a free-electron laser to scan across the entire region near the K-shell threshold. Furthermore, we find that the delay spectrum is richly modulated, suggesting several contributions, including transient trapping of the photoelectron owing to shape resonances, collisions with the Auger-Meitner electron that is emitted in the rapid non-radiative relaxation of the molecule and multi-electron scattering effects. The results demonstrate how X-ray attosecond experiments, supported by comprehensive theoretical modelling, can unravel the complex correlated dynamics of core-level photoionization.