# Streaking strong-field double ionization

## TL;DR

This paper demonstrates an all-optical streaking technique to measure electron emission times in strong-field double ionization, revealing differences between sequential and non-sequential processes through experimental and theoretical analysis.

## Contribution

It introduces a novel streaking method to directly access electron emission times in double ionization, distinguishing between different ionization mechanisms.

## Key findings

- Streaking delays differ between sequential and non-sequential double ionization.
- Coincidence detection reveals emission time differences from two-electron momentum distributions.
- Experimental results align well with simulations of sequential double ionization.

## Abstract

Double ionization in intense laser fields can comprise electron correlations, which manifest in the non-independent emission of two electrons from an atom or molecule. However, experimental methods that directly access the electron emission times have been scarce. Here, we explore the application of an all-optical streaking technique to strong-field double ionization both theoretically and experimentally. We show that both sequential and non-sequential double ionization processes lead to streaking delays that are distinct from each other and single ionization. Moreover, coincidence detection of ions and electrons provides access to the emission time difference, which is encoded in the two-electron momentum distributions. The experimental data agree very well with simulations of sequential double ionization. We further test and discuss the application of this method to non-sequential double ionization, which is strongly affected by the presence of the streaking field.