Resolved frustrated tunneling ionization in asymmetrical fast oscillation of above-threshold ionization spectrum

TL;DR

This paper reports the first experimental observation of asymmetrical fast oscillations in above-threshold ionization spectra of Argon, revealing the distinct roles of frustrated tunneling ionization and direct tunneling ionization.

Contribution

It provides the first experimental evidence to distinguish effects of FTI and DTI in ATI spectra through phase-dependent oscillations.

Findings

Observation of c/5 oscillation due to FTI interference

Asymmetry in ATI spectrum attributed to DTI

First experimental resolution of FTI and DTI effects

Abstract

Tunneling ionization is one of the fundamental electron dynamics, which has wide applications in ultrafast physics. When frustrated tunneling ionization (FTI) is considered, the tunneling rate is not equivalent to ionization rate. However, it is hard to resolve the effects of FTI and direct tunneling ionization (DTI) in ionization spectrum experimentally. Here we report the first observation of the asymmetrical fast oscillation in above-threshold ionization (ATI) spectrum of Argon as function of carrier-envelope phase (CEP), to the best of our knowledge. Simulation results identify that in the experimental ATI spectrum, the {\pi}/5 oscillation originates from the quantum interference of electrons in FTI, while DTI is responsible for the asymmetry. Our results provide clear evidence to resolve the effects of direct tunneling and FTI in a new physical regime.