Resolving Rydberg-Electron Recapture Dynamics via Laser-driven Frustrated Tunneling Ionization

TL;DR

This paper investigates Rydberg-electron recapture dynamics using two-color circularly polarized laser fields and coherent EUV emission, revealing that recapture mainly occurs at the end of the laser pulse, confirmed through experimental evidence.

Contribution

It provides the first direct experimental confirmation that Rydberg-electron recapture predominantly occurs at the end of the laser pulse, using novel laser field configurations and coherent emission measurements.

Findings

Distinct ellipticity dependence between XFID and high-order harmonic generation.

Recapture occurs mainly at the end of the laser pulse.

Differences in yield variations with laser intensity ratios.

Abstract

By employing two-color counter-rotating circularly polarized laser fields, we investigate the dynamics of electron recapture into Rydberg states under strong, ultrashort laser pulses, probed via coherent extreme-ultraviolet free-induction decay (XFID). Our study reveals significant distinctions between XFID and above-threshold high-order harmonic generation in terms of their ellipticity dependence on the driving-laser waveforms, yield variations with the laser-intensity ratios, and sensitivity to the driving-laser ellipticity. All these differences arise from the fundamentally distinct electron trajectories underlying the two processes. More importantly, our findings provide compelling evidence that Rydberg-electron recapture predominantly occurs at the end of the driving laser field, offering the first direct experimental confirmation of this long-proposed mechanism.