Attosecond dynamics through a Fano resonance: Monitoring the birth of a photoelectron

TL;DR

This paper demonstrates a spectrally-resolved electron interferometry technique that captures the amplitude and phase of a photoelectron wavepacket during autoionization in helium, enabling attosecond temporal resolution of electron dynamics.

Contribution

It introduces a novel experimental method to fully reconstruct the temporal evolution of autoionizing resonances using electron interferometry, advancing ultrafast quantum dynamics measurement.

Findings

Revealed the buildup of a Fano autoionizing resonance on attosecond timescales.

Achieved full temporal reconstruction of the resonant wavepacket from experimental data.

Confirmed results with ab initio time-dependent calculations.

Abstract

Amplitude and phase of wavepackets encode the dynamics of quantum systems. However, the rapidity of electron dynamics on the attosecond timescale has precluded their complete measurement in the time domain. Here, we demonstrate that spectrally-resolved electron interferometry reveals the amplitude and phase of a photoelectron wavepacket created through a Fano autoionizing resonance in helium. Replicas obtained by two-photon transitions interfere with reference wavepackets formed through smooth continua, allowing the full temporal reconstruction, purely from experimental data, of the resonant wavepacket released in the continuum. This in turn resolves the buildup of the autoionizing resonance on attosecond timescale. Our results, in excellent agreement with ab initio time-dependent calculations, raise prospects for both detailed investigations of ultrafast photoemission dynamics governed by electron correlation, as well as coherent control over structured electron wave-packets.