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State-resolved attosecond reversible and irreversible dynamics in strong optical fields


Strong-field ionization (SFI) is a key process for accessing real-time quantum dynamics of electrons on the attosecond timescale. The theoretical foundation of SFI was pioneered in the 1960s, and later refined by various analytical models. While asymptotic ionization rates predicted by these models have been tested to be in reasonable agreement for a wide range of laser parameters, predictions for SFI on the sub-laser-cycle timescale are either beyond the scope of the models or show strong qualitative deviations from full quantum-mechanical simulations. Here, using the unprecedented state specificity of attosecond transient absorption spectroscopy, we follow the real-time SFI process of the two valence spin–orbit states of xenon. The results reveal that the irreversible tunnelling contribution is accompanied by a reversible electronic population that exhibits an observable spin–orbit-dependent phase delay. A detailed theoretical analysis attributes this observation to transient ground-state polarization, an unexpected facet of SFI that cannot be captured by existing analytical models that focus exclusively on the production of asymptotic electron/ion yields.

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Figure 1: Experimental scheme and results.
Figure 2: Reconstructing experimental and theoretical effective Xe+ populations from ATAS spectrograms.
Figure 3: Comparing effective and instantaneous populations.
Figure 4: Decomposing the strong-field dynamics.
Figure 5: Time evolution of the charge density induced in Xe by a strong laser field in different intensity regimes.


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This material is based upon work supported by the National Science Foundation (NSF) (CHE-1361226) and the US Army Research Office (ARO) (W911NF-14-1-0383). Z.-H.L. acknowledges support from the Ministry of Education (MOE2014-T2-2-052) and the Agency for Science, Technology and Research (1223600008 and 1321202083). S.P. is funded by the Alexander von Humboldt Foundation and by the NSF through a grant to ITAMP.

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M.S. and H.T. performed the experiment and the data analysis. M.S., H.T., Z.-H.L., A.K.P. and S.G.S. designed and implemented the experimental set-up. Y.-J.C. conducted theoretical modelling, supported by S.P. and supervised by R.S. M.S., H.T. and Y.-J.C. wrote the manuscript, with input from all authors. The project was supervised by S.R.L.

Corresponding authors

Correspondence to Mazyar Sabbar or Stephen R. Leone.

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The authors declare no competing financial interests.

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Sabbar, M., Timmers, H., Chen, YJ. et al. State-resolved attosecond reversible and irreversible dynamics in strong optical fields. Nature Phys 13, 472–478 (2017).

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