Eur. Phys. J. Plus (2022) 137: 470
https://doi.org/10.1140/epjp/s13360-022-02695-7

Regular Article

Attosecond time shifts in atomic strong field ionization by tailored laser pulses

¹ Prokhorov General Physics Institute RAS, 119991, Moscow, Russia
² National Research Nuclear University MEPhI, Kashirskoe shosse 31, 115409, Moscow, Russia

^a sergey.popruzhenko@gmail.com

Received: 6 March 2022
Accepted: 5 April 2022
Published online: 15 April 2022

Abstract

Using the description of the ionization process in intense electromagnetic fields in terms of quantum orbits, we examine the ionization time concept used for the determination of the hypothetical tunneling time delay. We investigate the validity of the common conjecture that the electron escapes from the barrier with the highest probability when the electric field strength of the laser wave reaches its absolute maximum. Our calculation demonstrates that this is exactly correct either in the static field limit or under special restrictions imposed on the laser pulse shape, while for a laser pulse of an arbitrary form a small non-adiabatic time shift between the field maximum and the maximum of the tunneling probability emerges. For laser and atom parameters typical for experiments on tunnel or multiphoton ionization of atoms, this shift may vary from several to several dozens attoseconds. It also generates a potentially measurable correction in the angle between the directions of the most probable photoelectron momentum and of the highest electric field. Our findings may help identifying and measuring extremely small time and angular shifts in the strong field ionization process.