Attosecond multi-photon multi-electron dynamics

TL;DR

This paper demonstrates attosecond control over multi-photon multi-electron ionization processes in argon, revealing both sequential and simultaneous electron emission mechanisms on sub-femtosecond timescales.

Contribution

It introduces experimental evidence of controlling and distinguishing multi-electron ionization pathways using attosecond XUV pulses, advancing understanding of electron correlation dynamics.

Findings

Ar$^{2+}$ ionization is mainly sequential with weak delay dependence.

Ar$^{3+}$ ionization shows strong delay-dependent modulations.

Numerical calculations agree with experimental observations.

Abstract

Multi-electron dynamics in atoms and molecules very often occur on sub- to few-femtosecond timescales. The available intensities of extreme-ultraviolet (XUV) attosecond pulses have previously only allowed the time-resolved investigation of two-photon, two-electron interactions. Here we demonstrate attosecond control over double and triple ionization of argon atoms involving the absorption of up to five XUV photons. In an XUV-pump XUV-probe measurement using a pair of attosecond pulse trains (APTs), the Ar$^{2+}$ ion yield exhibits a weak delay dependence, showing that its generation predominantly results from the sequential emission of two electrons by photoabsorption from the two APTs. In contrast, the Ar$^{3+}$ ion yield exhibits strong modulations as a function of the delay, which is a clear signature of the simultaneous absorption of at least two XUV photons. The experimental results are well reproduced by numerical calculations that provide detailed insights into the ionization dynamics. Our results open up new opportunities for the investigation and control of multi-electron dynamics and complex electron correlation mechanisms on extremely short timescales.