Causality and quantum interference in time-delayed laser-induced nonsequential double ionization

Abstract

We perform a detailed analysis of the importance of causality within the strong-field approximation and the steepest descent framework for the recollision-excitation with subsequent tunneling ionization (RESI) pathway in laser-induced nonsequential double ionization (NSDI). In this time-delayed pathway, an electron returns to its parent ion, and, by recolliding with the core, gives part of its kinetic energy to excite a second electron at a time $t^{\prime }$. The second electron then reaches the continuum at a later time $t$ by tunneling ionization. We show that, if $t^{\prime }$ and $t$ are complex, the condition that recollision of the first electron occurs before tunnel ionization of the second electron translates into boundary conditions for the steepest-descent contours, and thus puts constraints on the saddles to be taken when computing the RESI transition amplitudes. We also show that this generalized causality condition has a dramatic effect in the shapes of the RESI electron momentum distributions for few-cycle laser pulses. Physically, causality determines how the dominant sets of orbits an electron returning to its parent ion can be combined with the dominant orbits of a second electron tunneling from an excited state. All features encountered are analyzed in terms of such orbits, and their quantum interference.

15 pages, 12 figures

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Cited by in corpus (11)

• Symphony on Strong Field Approximation
• Controlling Below-Threshold Nonsequential Double Ionization via Quantum Interference
• Quantum Interference in Time-Delayed Nonsequential Double Ionization
• Time-delayed nonsequential double ionization with few-cycle laser pulses: importance of the carrier-envelope phase
• Dialogue on analytical and ab initio methods in attoscience
• Temporal and spatial interference in molecular above-threshold ionization with elliptically polarized fields
• Restricted space ab initio models for double ionization by strong laser pulses
• Detangling the quantum tapestry of intra-channel interference in below-threshold nonsequential double ionization with few-cycle laser pulses
• Influence of catastrophes and hidden dynamical symmetries on ultrafast backscattered photoelectrons
• Unravelling inter-channel quantum interference in below-threshold nonsequential double ionization with statistical measures
• Physics-informed neural networks for solving saddle-point equations in strong-field physics with tailored fields