Tunneling ionization in ultrashort laser pulses: Edge effect and remedy

Abstract

Tunneling ionization of an atom in ultrashort laser pulses is considered. When the driving laser pulse is switched on and off with a steep slope, the photoelectron momentum distribution (PMD) shows an edge effect because of the photoelectron diffraction by the time slit of the pulse. The trivial diffraction pattern of the edge effect consisting of fast oscillations in the PMD disguises in the deep nonadiabatic regime the physically more interesting features in the spectrum, which originate from the photoelectron dynamics. We point out the precise conditions for how to avoid this scenario experimentally, and if unavoidable in theory we put forward an efficient method to remove the edge effect in the PMD. This allows us to highlight the nonadiabatic dynamical features of the PMD, which will be indispensable in additional investigations in complex computationally demanding scenarios. The method is first demonstrated with a one-dimensional problem, and further applied in three dimensions for the attoclock. The method is validated by a comparison of analytical results via the strong-field approximation with numerical solutions of the time-dependent Schrödinger equation.