Nondipole effects in tunneling ionization by intense laser pulses

TL;DR

This paper investigates nondipole effects in tunneling ionization caused by intense laser pulses, revealing how magnetic interactions influence ionization dynamics and providing a framework to incorporate these effects into semiclassical models.

Contribution

It introduces a nondipole strong-field approximation approach that accounts for magnetic effects beyond the electric dipole approximation in tunneling ionization.

Findings

Nondipole effects alter ionization rates and tunnel exit points.

Magnetic interactions influence electron momentum at tunneling.

The approach aligns with adiabatic limit results and identifies nonadiabatic initial condition modifications.

Abstract

The limit of decreasing laser frequency can not be considered independently from nondipole effects due to increase in the laser-induced continuum electron speed in this limit. Therefore, in this work, tunneling ionization in the adiabatic limit is considered for an effective field that includes effects beyond the electric-dipole term to first order in $1/c$, with $c$ the speed of light. The nondipole term describes the interaction resulting from the electric dipole-induced velocity of the electron and the magnetic field component of the laser. The impact of this term on the ionization rate, tunnel exit point, momentum at the tunnel exit and electron dynamics is discussed. In the appropriate limit, the results of a nondipole strong-field approximation approach and those of the strict adiabatic limit, where time and field strength are parameters, are consistent. The nondipole strong-field approximation approach is used to identify nonadiabatic modifications of the initial conditions. The results open up an avenue to include nondipole effects in the initial tunneling ionization step in semiclassical models of strong-field and attosecond physics.