Angle-resolved time delays for shake-up ionization of helium

TL;DR

This study reveals that shake-up ionization in helium exhibits significantly enhanced angle-dependent time delays due to dipolar coupling, with implications for understanding multi-electron dynamics in photoionization.

Contribution

It demonstrates that the angular variation of time delays in shake-up ionization is strongly affected by dipolar coupling, extending the additivity rule to angle-resolved RABBITT measurements.

Findings

Angular variation of time delay is dramatically enhanced by dipolar coupling.

Additivity rule for time delays remains valid for angle-resolved RABBITT.

Results applicable to other multi-electron, highly polarizable systems.

Abstract

Recent angle-resolved RABBITT experiments have shown that the photoionization time delay depends on the emission angle of the photoelectron. In this work we demonstrate that for photoemission from helium accompanied by shake-up (correlation satellites), the angular variation of the time delay is dramatically enhanced by the dipolar coupling between the photoelectron and the highly polarizable bound electron in the IR field. We show that the additivity rule for the time delays due to the atomic potential, the continuum-continuum (cc) coupling by the IR field, and due to this two-electron process remains valid for angle-resolved RABBITT. Our results are expected to be also applicable to other multi-electron systems that are highly polarizable or feature a permanent dipole moment.