Interpreting Attoclock Measurements of Tunnelling Times

Torlina, Lisa; Morales, Felipe; Kaushal, Jivesh; Müller, H. G.; Ivanov, Igor; Kheifets, Anatoli; Zielinski, Alejandro; Scrinzi, Armin; Sukiasyan, Suren; Ivanov, Misha; Smirnova, Olga

doi:10.48550/arxiv.1402.5620

Cited by 10 publications

(27 citation statements)

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“…Experimental separation of single ionization event requires application of very short pulses. Such pulses are available experimentally [1,2,5], but they may introduce additional envelopedependent effects [45], which are not considered here.…”

Section: Discussionmentioning

confidence: 99%

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Hole dynamics and spin currents after ionization in strong circularly polarized laser fields

Barth

Smirnova

2014

J. Phys. B: At. Mol. Opt. Phys.

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We apply the time-dependent analytical R-matrix theory to develop a movie of hole motion in a Kr atom upon ionization by strong circularly polarized field. We find rich hole dynamics, ranging from rotation to swinging motion. The motion of the hole depends on the final energy and the spin of the photoelectron and can be controlled by the laser frequency and intensity. Crucially, hole rotation is a purely non-adiabatic effect, completely missing in the framework of quasistatic (adiabatic) tunneling theories. We explore the possibility to use hole rotation as a clock for measuring ionization time. Analysing the relationship between the relative phases in different ionization channels we show that in the case of short-range electroncore interaction the hole is always initially aligned along the instantaneous direction of the laser field, signifying zero delays in ionization. Finally, we show that strong-field ionization in circular fields creates spin currents (i.e. different flow of spin-up and spin-down density in space) in the ions. This phenomenon is intimately related to the production of spin-polarized electrons in strong laser fields Phys. Rev. A 88 013401]. We demonstrate that rich spin dynamics of electrons and holes produced during strong field ionization can occur in typical experimental conditions and does not require relativistic intensities or strong magnetic fields.

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Section: Discussionmentioning

confidence: 99%

“…Initial mismatch between these directions could indicate ionization delays. Since ionization delay is strictly zero for short range potentials [45], we expect the hole to be aligned along the direction of the laser field.…”

Section: Initial Alignment Of the Holementioning

confidence: 99%

Hole dynamics and spin currents after ionization in strong circularly polarized laser fields

Barth

Smirnova

2014

J. Phys. B: At. Mol. Opt. Phys.

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“…In this letter we put foward an intuitive picture for the intermediate regime of ionization describing it as tunneling through a classically forbidden region with a coordinate dependent rising energy due to the time-dependent barrier. The picture allows to deduce in a simple way the characteristics of the under-the-barrier motion and shows how the semi-classical theory of [5] should be remedied to describe the observed photoelectron spectra, explaining the discrepancy between results of [5] and [24]. Nonadiabatic effects induce a transversal momentum shift of the electron at the tunneling exit, a delayed appearance in the continuum as well as a shift of the tunneling exit coordinate towards the ionic core.…”

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confidence: 95%

“…Recent experimental investigations of nonadiabatic effects for the attoclock calibration indicated no significant impact of these effects on the distribution of the photoelectron momentum up to a Keldysh parameter of γ ≈ 3.8 [5] and the difference between the quasi-static calculations and experimental results was attributed to a tunneling delay time. However, numerical simulations [22] and a R-matrix theory calculation [23] concluded that the observed photoelectron emission momentum distribution are explainable with a vanishing tunneling time delay when the Coulomb field of the atomic core is fully taken into account [24].…”

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confidence: 99%

Tunneling Dynamics in Multiphoton Ionization and Attoclock Calibration

2015

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The intermediate domain of strong-field ionization between the tunneling and multiphoton regimes is investigated using the strong-field approximation and the imaginary-time method. An intuitive model for the dynamics is developed which describes the ionization process within a nonadiabatic tunneling picture with a coordinate dependent electron energy during the under-the-barrier motion. The nonadiabatic effects in the elliptically polarized laser field induce a transversal momentum shift of the tunneled electron wave packet at the tunnel exit and a delayed appearance in the continuum as well as a shift of the tunneling exit towards the ionic core. The latter significantly modifies the Coulomb focusing during the electron excursion in the laser field after exiting the ionization tunnel. We show that nonadiabatic effects are especially large when the Coulomb field of the ionic core is taken into account during the under-the-barrier motion. The simple man model modified with these nonadiabatic corrections provides an intuitive background for exact theories and has direct implications for the calibration of the attoclock technique.

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“…Measurements of strongfield ionization have revealed complex and surprising qualitative features [5,6] that can depend sensitively on the laser intensity. Precise measurements of strongfield ionization are now being used to probe fundamental physics, such as time delays in photoionization [7], but there is substantial evidence that small systematic offsets in these measurements can obscure the results [8]. In frequency metrology, measurements of atomic transitions are affected by systematic errors arising from the AC-Stark shift and laser intensity uncertainty, thereby limiting the precision of the result [9].…”

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confidence: 99%