Attosecond electron spectroscopy using a novel interferometric pump-probe technique

TL;DR

This paper introduces a novel interferometric pump-probe method for attosecond electron spectroscopy, enabling high-resolution characterization of electron wave packets by using a free wave as a reference.

Contribution

The paper presents a new interferometric technique that uses a free electron wave as a reference to measure bound electron wave packets with unprecedented spectral resolution.

Findings

Successfully demonstrated the method with helium atoms

Achieved spectral resolution surpassing the inverse of the pulse duration

Captured quantum beats and multi-path interference in the interferogram

Abstract

We present an interferometric pump-probe technique for the characterization of attosecond electron wave packets (WPs) that uses a free WP as a reference to measure a bound WP. We demonstrate our method by exciting helium atoms using an attosecond pulse with a bandwidth centered near the ionization threshold, thus creating both a bound and a free WP simultaneously. After a variable delay, the bound WP is ionized by a few-cycle infrared laser precisely synchronized to the original attosecond pulse. By measuring the delay-dependent photoelectron spectrum we obtain an interferogram that contains both quantum beats as well as multi-path interference. Analysis of the interferogram allows us to determine the bound WP components with a spectral resolution much better than the inverse of the attosecond pulse duration.