Role of intermediate resonances in attosecond photoelectron interferometry in neon

TL;DR

This paper investigates how intermediate resonances influence attosecond photoelectron interferometry in neon, revealing their significant impact on phase and angular distributions, and demonstrating control over resonance contributions by tuning photon energies.

Contribution

It introduces a method to analyze and control the effects of intermediate resonances in attosecond photoelectron interferometry using neon.

Findings

Resonances significantly alter phase and angular distributions.

Tuning harmonic photon energies can enhance or suppress specific resonances.

Intermediate states imprint large phases on photoelectron wave packets.

Abstract

Attosecond photoelectron interferometry based on the combination of an attosecond pulse train and a synchronized infrared field is a fundamental technique for the temporal characterization of attosecond waveforms and for the investigation of electron dynamics in the photoionization process. In this approach, the comb of extreme ultraviolet harmonics typically lies above the ionization threshold of the target under investigation, thus releasing a photoelectron by single-photon absorption. The interaction of the outgoing photoelectron with the infrared pulse results in the absorption or emission of infrared photons, thereby creating additional peaks in the photoelectron spectrum, referred to as sidebands. While, in the absence of resonances in the first ionization step, the phases imparted on the photoionization process evolve smoothly with the photon energy, the presence of intermediate resonances imprints a large additional phase on the outgoing photoelectron wave packet. In this work, using a comb of harmonics below and above the ionization threshold of neon, we investigate the effect of intermediate bound excited states on attosecond photoelectron interferometry. We show that the phase of the oscillations of the sidebands and their angular distributions are strongly affected by such resonances. By slightly tuning the photon energies of the extreme ultraviolet harmonics, we show how the contributions of selected resonances can be enhanced or suppressed.