Phase evolution of strong-field ionization

TL;DR

This paper explores the ultrafast evolution of dipole phase shifts caused by strong-field ionization in xenon, using attosecond transient absorption spectroscopy to reveal complex dynamics involving ionization, transient populations, and polarization effects.

Contribution

It provides new insights into the attosecond-scale phase dynamics of strong-field ionization, combining experimental measurements with theoretical calculations.

Findings

Identification of three key processes influencing phase evolution

Observation of complex, attosecond-scale dynamics in xenon

Correlation between ionization, population, and polarization effects

Abstract

We investigate the time-dependent evolution of the dipole phase shift induced by strong-field ionization (SFI) using attosecond transient absorption spectroscopy (ATAS) for time-delays where the pump-probe pulses overlap. We study measured and calculated time-dependent ATA spectra of the ionic 4d-5p transition in xenon, and present the time-dependent line shape parameters in the complex plane. We attribute the complex, attosecond-scale dynamics to the contribution of three distinct processes: accumulation of ionization, transient population, and reversible population of excited states arising from polarization of the ground state.