Tunneling Dynamics in Multiphoton Ionization and Attoclock Calibration

Abstract

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.

Ionization Time and Exit Momentum in Strong-Field Tunnel Ionization

“…Similarly to the delay τ 2 , also the time delays determined from measured asymptotic momenta are close to zero (of the order of experimental uncertainties) [10,11]. As our numerical calculations indicate that the reconstruction of the delay τ A from asymptotic momenta is sensitive to the electron's exit momentum, we argue that a possible nonzero exit momentum into the electric field direction has to be included for a reliable reconstruction of τ A in attoclock experiments, not only a nonzero exit momentum in the direction perpendicular to the electric field as recently proposed [20,39].…”

Journeys from quantum optics to quantum technology

“…An example project considered how the tunneling process was affected by magnetic fields and an adapted gauge invariant tunnelling picture was developed [76]. In addition the non-adiabatic regime was investigated [77] and the tunnelling time was evaluated [78] and just confirmed experimentally with our local colleagues in Heidelberg [79].…”

Above-threshold ionization with highly charged ions in superstrong laser fields. III. Spin effects and their dependence on laser polarization

“…2, where the final momentum distribution is calculated numerically via Eq. (80). We emphasize that the momentum distribution (96) is valid also for an arbitrarily elliptical polarization with an ellipticity 0 ζ 1.…”