Tunneling criteria and a nonadiabatic term for strong-field ionization

Ni, Hongcheng; Eicke, Nicolas; Ruiz, Camilo; Cai, J.; Oppermann, Florian; Shvetsov-Shilovski, N. I.; Pi, Liang-Wen

doi:10.1103/physreva.98.013411

Cited by 60 publications

(71 citation statements)

References 49 publications

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“…Tunneling is a QMal manifestation and a classical point of view is not appropriate anyway, a deterministic T-time is not expected. Furthermore, although they found a positive time at the exit point by back propagating with the position-based criterion, they claimed that the T-time is zero and the criterion can be considered as a misinterpretation of the attoclock experimental data based on models that do not take full and consistent account for nonadiabaticity, with the argument that they found a high non-tunneled fraction [70], we come back later to this important point. In the same work [69], they found that a static energy-based (again in their notation) adiabatic tunneling criterion fails completely.…”

Section: Attoclock and Tunneling Time In Strong Field Interactionmentioning

confidence: 71%

Time Operator, Real Tunneling Time in Strong Field Interaction and the Attoclock

Kullie

2020

Quantum Reports

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Attosecond science, beyond its importance from application point of view, is of a fundamental interest in physics. The measurement of tunneling time in attosecond experiments offers a fruitful opportunity to understand the role of time in quantum mechanics. In the present work, we show that our real T-time relation derived in earlier works can be derived from an observable or a time operator, which obeys an ordinary commutation relation. Moreover, we show that our real T-time can also be constructed, inter alia, from the well-known Aharonov-Bohm time operator. This shows that the specific form of the time operator is not decisive, and dynamical time operators relate identically to the intrinsic time of the system. It contrasts the famous Pauli theorem, and confirms the fact that time is an observable, i.e., the existence of time operator and that the time is not a parameter in quantum mechanics. Furthermore, we discuss the relations with different types of tunneling times, such as Eisenbud-Wigner time, dwell time, and the statistically or probabilistic defined tunneling time. We conclude with the hotly debated interpretation of the attoclock measurement and the advantage of the real T-time picture versus the imaginary one.

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Section: Attoclock and Tunneling Time In Strong Field Interactionmentioning

confidence: 71%

Time Operator, Real Tunneling Time in Strong Field Interaction and the Attoclock

Kullie

2020

Quantum Reports

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“…Strong-field ionisation is one of the most studied phenomena that occur when matter interacts with intense laser fields. Not only does it invite fundamental questions, such as the measurement and the criteria for determining tunnelling times [1][2][3][4][5][6], but, in addition, it gave rise to whole research areas. Examples are laser-induced electron diffraction [7], or ultrafast photoelectron holography [8,9]; for a review see [10].…”

Section: Introductionmentioning

confidence: 99%

Quantum bridges in phase space: interference and nonclassicality in strong-field enhanced ionisation

2019

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We perform a phase-space analysis of strong-field enhanced ionisation in molecules, with emphasis on quantum-interference effects. Using Wigner quasi-probability distributions and the quantum Liouville equation, we show that the momentum gates reported in a previous publication (Takemoto and Becker 2011 Phys. Rev. A 84 023401) may occur for static driving fields, and even for no external field at all. Their primary cause is an interference-induced bridging mechanism that occurs if both wells in the molecule are populated. In the phase-space regions for which quantum bridges occur, the Wigner functions perform a clockwise rotation whose period is intrinsic to the molecule. This evolution is essentially non-classical and non-adiabatic, as it does not follow equienergy curves or field gradients. Quasi-probability transfer via quantum bridges is favoured if the electron's initial state is either spatially delocalised, or situated at the upfield molecular well. Enhanced ionisation results from the interplay of this cyclic motion, adiabatic tunnel ionisation and population trapping. Optimal conditions require minimising population trapping and using the bridging mechanism to feed into ionisation pathways along the field gradient.

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“…It exploits the fact that in strong-field above-threshold ionization (ATI) of atoms with circularly polarized laser fields, the ionization time of the photoelectron is mapped to its detection angle. First implemented by Eckle et al [1], it was subsequently used to probe ionization time delays, Coulomb effects, spatial properties of the tunnel barrier, and multielectron effects [2][3][4][5][6][7][8][9][10]. Detailed knowledge about the ionization step is important as it is the first part of the three-step process that leads to high-harmonic generation (HHG) and laser-induced electron diffraction or rescattering [11][12][13][14][15][16][17], and to set the initial conditions for trajectory-based models of strong-field ionization [18][19][20].…”

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confidence: 99%

“…To make a further comparison, the bicircular attoclock also allows us to apply classical backpropagation [8][9][10] to quasilinear polarization. In previous works, it has only been implemented for circular polarization.…”

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confidence: 99%

Attoclock with counter-rotating bicircular laser fields

Eicke

Lein

2019

Phys. Rev. A

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The attoclock technique which maps the emission time of a photoelectron to its detection angle is an important tool in strong-field physics. Previously, it was implemented only with circularly or elliptically polarized laser fields. Here, we show how counter-rotating bicircular laser fields can be used as an attoclock to investigate the ionization dynamics in quasilinear polarization. This is achieved by choosing the ratio of the two field strengths in a way such that the vector potential has aspects of the attoclock and time is mapped directly to the photoelectron momentum, but the shape of the electric field corresponds to approximately linear polarization during three intervals per optical cycle. We report momentum distributions calculated by solving the time-dependent Schrödinger equation for a model helium atom and obtain the mapping from photoelectron momentum to ionization time using a trajectory-free method. Unlike circular polarization where the time of maximal ionization rate typically deviates less than 5 attoseconds from the maximium of the electric field, we find positive ionization times of more than 10 attoseconds in the quasilinear case.

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Tunneling criteria and a nonadiabatic term for strong-field ionization

Cited by 60 publications

References 49 publications

Time Operator, Real Tunneling Time in Strong Field Interaction and the Attoclock

Time Operator, Real Tunneling Time in Strong Field Interaction and the Attoclock

Quantum bridges in phase space: interference and nonclassicality in strong-field enhanced ionisation

Attoclock with counter-rotating bicircular laser fields

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