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Attosecond real-time observation of electron tunnelling in atoms


Atoms exposed to intense light lose one or more electrons and become ions. In strong fields, the process is predicted to occur via tunnelling through the binding potential that is suppressed by the light field near the peaks of its oscillations. Here we report the real-time observation of this most elementary step in strong-field interactions: light-induced electron tunnelling. The process is found to deplete atomic bound states in sharp steps lasting several hundred attoseconds. This suggests a new technique, attosecond tunnelling, for probing short-lived, transient states of atoms or molecules with high temporal resolution. The utility of attosecond tunnelling is demonstrated by capturing multi-electron excitation (shake-up) and relaxation (cascaded Auger decay) processes with subfemtosecond resolution.

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Figure 1: Strong-field ionization and pump-probe setting for its real-time observation.
Figure 2: Probing electron dynamics in atoms, molecules or solids with attosecond sampling techniques.
Figure 4: Ne 2+ ion yield versus delay between the subfemtoscond XUV pump and the few-cycle NIR probe: experiment and modelling.
Figure 3: Energy levels and transitions in Ne 1+ and Ne 2+ ions relevant to this study.
Figure 5: Energy levels and transitions in xenon ions relevant to the current study.
Figure 6: Xe 4+ and Xe 3+ ion yields versus delay between the subfemtosecond XUV pump and the few-cycle NIR probe.

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We thank A. F. Starace for discussions. We are grateful for financial support from the Volkswagenstiftung (Germany), the Marie Curie Research Training Network XTRA, Laserlab Europe, and a Marie Curie Intra-European Fellowship. F.K. acknowledges support from the FWF (Austria). The research of M.F.K. and M.J.J.V. is part of the research programme of the Stichting voor Fundamenteel Onderzoek der Materie, which is financially supported by the Nederlandse Organisatie voor Wetenschappelijk Onderzoek. This research was supported by the cluster of excellence Munich Centre for Advanced Photonics (

Author Contributions M.U., Th.U., M.S. and A.J.V. contributed equally to this work.

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Correspondence to M. Uiberacker or F. Krausz.

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This file contains Supplementary Discussion, Supplementary Figures 1-11 with Legends, Supplementary Table 1 and additional references. The Supplementary Information concerns Setup, Data analysis and Simulations (PDF 930 kb)

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Uiberacker, M., Uphues, T., Schultze, M. et al. Attosecond real-time observation of electron tunnelling in atoms. Nature 446, 627–632 (2007).

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