Time Correlation Filtering Reveals Two-Path Electron Quantum Interference in Strong-Field Ionization

TL;DR

This paper introduces a differential Fourier analysis method to determine ionization time separations in strong-field ionization, revealing detailed electron interference patterns and validating results with Coulomb quantum orbit simulations.

Contribution

It presents a novel technique for extracting time correlations in electron trajectories from photoelectron spectra, enhancing analysis of strong-field ionization holography.

Findings

Identified electron holograms with various ionization time separations

Successfully compared experimental data with Coulomb quantum orbit model

Demonstrated the technique's applicability to diverse datasets

Abstract

Attosecond dynamics in strong-field tunnel ionization are encoded in intricate holographic patterns in the photoelectron momentum distributions (PMDs). These patterns show the interference between two or more superposed quantum electron trajectories, which are defined by their ionization times and subsequent evolution in the laser field. We determine the ionization time separation between interfering pairs of electron orbits by performing a differential Fourier analysis on the measured momentum spectrum. We identify electron holograms formed by trajectory pairs whose ionization times are separated by less than a single quarter cycle, between a quarter cycle and half cycle, between a half cycle and three fourths of a cycle, and a full cycle apart. We compare our experimental results to the predictions of the Coulomb quantum orbit strong-field approximation (CQSFA), with significant success. We also time-filter the CQSFA trajectory calculations to demonstrate the validity of the technique on spectra with known time correlations. As a general analysis technique, the filter can be applied to all energy- and angularly-resolved datasets to recover time correlations between interfering electron pathways, providing an important tool to analyze any strong-field ionization spectra.