Photoionization time delays probe electron correlations

TL;DR

This paper investigates how electron correlations influence photoionization time delays in multi-electron atoms, combining high-resolution experiments and advanced theory to deepen understanding of electron dynamics during ionization.

Contribution

It introduces a novel approach that combines attosecond interferometry with theoretical calculations to identify key electron correlations affecting photoemission.

Findings

Identification of essential electron correlations in photoionization

Unprecedented insight into atomic potential and electron dynamics

Resolution of discrepancies between previous experiments and theory

Abstract

The photoelectric effect, explained by Einstein in 1905, is often regarded as a one-electron phenomenon. However, in multi-electron systems, the interaction of the escaping electron with other electrons, referred to as electron correlation, plays an important role. For example, electron correlations in photoionization of the outer $s$-subshells of rare gas atoms lead to a substantial minimum in the ionization probability, which was theoretically predicted in 1972 and experimentally confirmed using synchrotron radiation. However, recent attosecond photoionization time delay measurements in argon strongly disagree with theory, thus raising questions on the nature of electron correlations leading to this minimum. In this work, combining high-spectral resolution attosecond interferometry experiments and novel theoretical calculations allows us to identify the most essential electron correlations affecting the photoemission. The measurement of time delays gives unprecedented insight into the photoionization process, unraveling details of the atomic potential experienced by the escaping electron and capturing its dynamics.