Nondipole Coulomb sub-barrier ionization dynamics and photon momentum sharing

TL;DR

This paper investigates how the Coulomb field influences electron dynamics during strong-field tunneling ionization, revealing that sub-barrier Coulomb effects increase photon momentum sharing along the laser propagation direction, with implications for experimental observations.

Contribution

It extends the strong field approximation to include non-dipole Coulomb corrections, showing the counter-intuitive effect of the sub-barrier Coulomb field on electron momentum shifts.

Findings

Sub-barrier Coulomb field increases longitudinal momentum shift.

The effect depends on laser field strength and atomic quantum numbers.

Signature detectable via asymptotic photoelectron momentum distribution.

Abstract

The nondipole under-the-barrier dynamics of the electron during strong-field tunneling ionization is investigated, examining the role of the Coulomb field of the atomic core. The common analysis in the strong field approximation is consequently generalised to include the leading light-front non-dipole Coulomb corrections and demonstrates the counter-intuitive impact of the sub-barrier Coulomb field. Despite its attractive nature, the sub-barrier Coulomb field increases the photoelectron nondipole momentum shift along the laser propagation direction, involving a strong dependence on the laser field. The scaling of the effect with respect to the principal quantum number and angular momentum of the bound state is found. We demonstrate that the signature of Coulomb induced sub-barrier effects can be identified in the asymptotic photoelectron momentum distribution via a comparative study of the field-dependent longitudinal momentum shift for different atomic species with state-of-the-art experimental techniques of mid-infrared lasers.