Control of the Ion Polarization in the Pump-Probe Ionization of Helium

TL;DR

This paper investigates how to control the coherence of Helium ion states during pump-probe ionization using an ab initio time-dependent approach, revealing periodic dipole revivals on a picosecond scale.

Contribution

It introduces a method to manipulate ion coherence in Helium through pulse sequence parameters, advancing control in attosecond ionization processes.

Findings

Periodic revivals of ion dipole moment observed

Control of ion coherence achieved via pulse parameters

Insights into ionization of oriented targets obtained

Abstract

Attosecond pump-probe ionization process can be used to prepare atomic ions in the coherent superposition of states with opposite parity. The multiphoton shake-up ionization of Helium, in particular, generates ions with same principal quantum number and a net dipole moment that evolves on a time scale of few picoseconds, due to spin-orbit coupling. In this work we use an ab initio time-dependent close-coupling code to study how the coherence between levels of Helium ion can be controlled from the parameters of the ionizing-pulse sequence. The observed periodic revivals, on a picosecond time scale, of the ion dipole moment gives access to the study of the ionization of oriented targets.