Strongly driven molecules: probing the tunneling phase in the over-the-barrier regime and prevalence of different double ionization pathways

TL;DR

This study uses a three-dimensional quasiclassical approach to analyze molecular double ionization across different laser intensities, revealing how ionization pathways and tunneling phases vary from tunneling to over-the-barrier regimes.

Contribution

It provides a unified analysis of double ionization pathways and introduces a method to directly verify the tunneling phase of re-colliding electrons in different regimes.

Findings

Identification of double ionization pathways as a function of total energy.

Demonstration of tunneling phase differences between regimes.

Correlation between electron momenta and ionization probability distributions.

Abstract

Using a three-dimensional quasiclassical technique we explore molecular double ionization by a linearly polarized, infrared (800~nm) 27~fs laser pulse. For intensities ranging from the tunneling to the over-the-barrier regime, we identify the double ionization pathways in a unified way as a function of total electron energy. For the tunneling regime, we discuss the differences in the interplay of double ionization (DI) pathways between strongly driven He and strongly driven $N_{2}$. For intermediate intensities in the over-the-barrier regime, we find that both the correlated momenta and the double ionization probability distribution as a function of total energy probe the tunneling phase of the re-colliding electron. This allows for a direct verification of the re-colliding electron tunneling at a large phase of the laser field in the over-the-barrier regime in contrast to a small tunneling phase in the tunneling regime.