Direct Experimental Access to the Nonadiabatic Initial Momentum Offset upon Tunnel Ionization

Eckart, Sebastian; Fehre, K.; Eicke, Nicolas; Hartung, Alexander; Rist, J.; Trabert, D.; Strenger, N.; Pier, Andreas; Schmidt, L. Ph. H.; Jahnke, T.; Schöffler, M. S.; Lein, Manfred; Kunitski, Maksim; Dørner, R.

doi:10.1103/physrevlett.121.163202

Cited by 62 publications

(48 citation statements)

References 36 publications

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“…A significant part of this fall is reproduced by the SPM cal-culation simply because the SP equation (6), which can be understood as the energy conservation at the exit from the tunnel, contains an additional kinetic energy term k 2 z /2. This increases an effective ionization potential [34] and thus reduces Im t s as illustrated on the top diagram of Fig. 2 (filled symbols at k z = 0 versus open symbols at k z = 1 au).…”

Section: B Semi-classical Approachmentioning

confidence: 94%

Numerical attoclock on atomic and molecular hydrogen

2019

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Numerical attoclock is a theoretical model of attosecond angular streaking driven by a very short, nearly a single oscillation, circularly polarized laser pulse. The reading of such an attoclock is readily obtained from a numerical solution of the time-dependent Schrödinger equation as well as a semi-classical trajectory simulation. By making comparison of the two approaches, we highlight the essential physics behind the attoclock measurements. In addition, we analyze the predictions the Keldysh-Rutherford model of the attoclock [Phys. Rev. Lett. 121, 123201 (2018)]. In molecular hydrogen, we highlight a strong dependence of the width of the attoclock angular peak on the molecular orientation and attribute it to the two-center electron interference. This effect is further exemplified in the weakly bound neon dimer. 32.80.Fb The experimental technique of attosecond angular streaking (attoclock) is based on measuring an offset angle of the peak photoelectron momentum distribution (PMD) in the polarization plane of a close-to-circularly polarized laser pulse. The attoclock attempts to relate this offset angle with the time the tunneling electron spends under the barrier (tunneling time) [1][2][3][4]. As the tunneling is an exponentially suppressed process, it occurs predominantly at the peak of the driving laser pulse. At this instant, the electric field is aligned with the major axis of the polarization ellipse. The photoelectron emerges from the tunnel with the zero velocity and its canonical momentum captures the vector potential of the laser field at the time of exit. This momentum is carried to the detector and its angular displacement relative to the minor polarization axis is converted to the tunneling time τ = θ A /ω, where ω is the angular frequency of the driving field. A similar attoclock reading θ A can be obtained from numerical simulations with very short, nearly single oscillation, circularly polarized pulses. The utility of such a "numerical attoclock" is that it allows for treatment by various simplified, but more physically transparent, techniques such as an analytic R-matrix theory [5], a classical back-propagation analysis [6], classical-trajectory Monte Carlo simulations [7] and a classical Rutherford scattering model [8]. By making comparison with these models, numerical attoclock experiments firmly point to a vanishing tunneling time [5,6,8]. Similar conclusion was also reached in recent theoretical [9, 10] and experiemntal [11] works. The debate of the finite tunneling time is still open. Some authors continue to advocate a finite tunneling time [12][13][14] while others suggest that the whole concept is ill defined and no meaningful definition of the tunneling time can be given [15].Irrespective of the answer to the tunneling time conundrum, the principle of attoclock remains appealing and finds its application to more complex targets. In particular, there have been preliminary reports of attosecond angular streaking measurements on molecular hydrogen [16,17]. Coincident detection of pho...

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Section: B Semi-classical Approachmentioning

confidence: 94%

Numerical attoclock on atomic and molecular hydrogen

2019

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“…accounts for the width of the initial momentum distribution after tunneling [24] and p 0 = 0.2 a.u. is chosen to model a typical nonadiabatic momentum offset [25][26][27]. The result is shown as | lin,env | 2 in Fig.…”

Section: Numerical Examples With Offset Phasementioning

confidence: 99%

Holographic angular streaking of electrons and the Wigner time delay

Eckart

2020

Phys. Rev. Research

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For a circularly polarized single-color field at a central frequency of 2ω, the final electron momentum distribution upon strong field ionization does not carry any information about the phase of the initial momentum distribution. Adding a weak, corotating, circularly polarized field at a central frequency of ω gives rise to a subcycle interference pattern [holographic angular streaking of electrons (HASE)]. This interference pattern allows for the retrieval of the derivative of the phase of the initial momentum distribution after tunneling φ off (p i). A trajectory-based semiclassical model (HASE model) is introduced which links the experimentally accessible quantities to φ off (p i). It is shown that a change in φ off is equivalent to a displacement in position space x of the initial wave packet after tunneling. This offset in position space allows for an intuitive interpretation of the Wigner time delay τ W in strong-field ionization for circularly polarized single-color fields. The influence of Coulomb interaction after tunneling is investigated quantitatively.

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“…For single ionization by elliptically polarized light, the major axis of the polarization ellipse is a natural reference. The emission angle ϕ in the polarization plane encodes a combination of the birth time and the initial momentum of the wave packet [11] as well as its interaction with the ionic potential. It is this coordinate in which we search for a chiral signature.…”

Section: Introductionmentioning

confidence: 99%

Angular streaking in strong field ionization of chiral molecules

Fehre

Eckart

Kunitski

et al. 2019

Phys. Rev. Research

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We report on a chiral observable upon ionization of a chiral molecule (methyloxirane) by a strong elliptically polarized laser field: a rotation of the photoelectron momentum distribution, which is enantiosensitive and forward/backward asymmetric. We explain this forward/backward asymmetric rotation of the count maxima to be equivalent to a dependence of the photoelectron circular dichroism on the electron emission angle in the plane of polarization.

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Direct Experimental Access to the Nonadiabatic Initial Momentum Offset upon Tunnel Ionization

Cited by 62 publications

References 36 publications

Numerical attoclock on atomic and molecular hydrogen

Numerical attoclock on atomic and molecular hydrogen

Holographic angular streaking of electrons and the Wigner time delay

Angular streaking in strong field ionization of chiral molecules

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