Probing time-ordering in two-photon double ionization of helium on the attosecond time scale

TL;DR

This paper demonstrates how attosecond streaking can be used to measure the time ordering and delays in two-photon double ionization of helium, providing new insights into ultrafast electron dynamics.

Contribution

It introduces a method to extract time ordering and delays in two-electron emission processes using attosecond streaking, supported by ab-initio simulations.

Findings

Time delays depend on electron energy, pulse duration, and emission angles.

Attosecond streaking can unambiguously determine emission time intervals.

Benchmark data for experimental observables in two-photon double ionization.

Abstract

We show that time ordering underlying time-dependent quantum dynamics is a physical observable accessible by attosecond streaking. We demonstrate the extraction of time ordering for the prototypical case of time-resolved two-photon double ionization (TPDI) of helium by an attosecond XUV pulse. The Eisenbud-Wigner-Smith time delay for the emission of a two-electron wavepacket and the time interval between subsequent emission events can be unambiguously determined by attosecond streaking. The delay between the two emission events sensitively depends on the energy, pulse duration, and angular distribution of the emitted electron pair. Our fully-dimensional ab-initio quantum mechanical simulations provide benchmark data for experimentally accessible observables.