Nondipole strong-field approximation for above-threshold ionization in a few-cycle pulse

Abstract

The ionization of atoms and molecules by strong laser fields has been studied extensively, both theoretically and experimentally. The strong-field approximation (SFA) allows for the analytical solution of the Schr\"odinger equation and accurately predicts the behavior of ionization processes in intense laser fields. Over the past decade, there has been a growing interest in the study of nondipole effects in these processes. However, such predictions have so far been limited to monochromatic driving laser fields, while experiments often employ quite short pulses. In this paper, we therefore present an extension of the SFA that also allows incorporating the more complicated temporal structure of a few-cycle pulse. By this extension, the prediction of so-called peak shifts is significantly improved, and the ability to control the laser pulse inducing above-threshold ionization is greatly enhanced. The enhanced control over the characteristics of the laser pulse results in more accurate predictions of peak shifts. Our results show better agreement with experimental investigations compared to previous theoretical studies.