Laser-driven recollisions under the Coulomb barrier

Abstract

Photoelectron spectra obtained from the ab initio solution of the time-dependent Schrödinger equation can be in striking disagreement with predictions by the strong-field approximation (SFA) not only at low energy but also around twice the ponderomotive energy where the transition from the direct to the rescattered electrons is expected. In fact, the relative enhancement of the ionization probability compared to the SFA in this regime can be several orders of magnitude. We show for which laser and target parameters such an enhancement occurs and for which the SFA prediction is qualitatively good. The enhancement is analyzed in terms of the Coulomb-corrected action along analytic quantum orbits in the complex-time plane, taking soft recollisions under the Coulomb barrier into account. These recollisions in complex time and space prevent a separation into sub-barrier motion up to the "tunnel exit" and subsequent classical dynamics. Instead, the entire quantum path up to the detector determines the ionization probability.

5 pages, 2 figures, RevTeX 4.1

References in corpus (7)

• Low-Energy Structures in Strong Field Ionization Revealed by Quantum Orbits
• Intracycle and Intercycle Interferences in Above-Threshold Ionization: the Time Grating
• Strong Field Approximation for Systems with Coulomb Interaction
• Origin of Unexpected Low Energy Structure in Photoelectron Spectra Induced by Mid-Infrared Strong Laser Fields
• Electron-energy bunching in laser-driven soft recollisions
• Non-adiabatic Coulomb effects in strong field ionisation in circularly polarised laser fields
• Slalom in complex time: emergence of low-energy structures in tunnel ionization via complex time contours

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• Analytical approach to Coulomb focusing in strong field ionization
• The imaginary part of the high-harmonic cutoff
• Nondipole Coulomb sub-barrier ionization dynamics and photon momentum sharing
• Origin of high energy enhancement of photoelectron spectra in tunneling ionization
• Numerical time-of-flight analysis of the strong-field photoeffect
• Relativistic analytical R-matrix (ARM) theory for strong-field ionization
• Entropy-based view of the strong field ionization process