Time-frequency representations of autoionization dynamics in helium

TL;DR

This paper investigates autoionization in helium by measuring spectral amplitude and phase of emitted wavepackets, enabling detailed analysis of the underlying electron dynamics through advanced interferometric and time-frequency techniques.

Contribution

It introduces an energy-resolved interferometric method to measure spectral amplitude and phase of autoionized wavepackets, revealing detailed temporal and frequency dynamics.

Findings

Reconstructed temporal profiles of autoionized wavepackets.

Visualized the buildup of wavepackets in the continuum.

Disentangled direct and resonant ionization channel dynamics.

Abstract

Autoionization, which results from the interference between direct photoionization and photoexcitation to a discrete state decaying to the continuum by configuration interaction, is a well known example of the important role of electron correlation in light-matter interaction. Information on this process can be obtained by studying the spectral, or equivalently, temporal complex amplitude of the ionized electron wavepacket. Using an energy-resolved interferometric technique, we measure the spectral amplitude and phase of autoionized wavepackets emitted via the sp2+ and sp3+ resonances in helium. These measurements allow us to reconstruct the corresponding temporal profiles by Fourier transform. In addition, applying various time-frequency representations, we observe the build up of the wavepackets in the continuum, monitor the instantaneous frequencies emitted at any time and disentangle the dynamics of the direct and resonant ionization channels.