Probing the longitudinal momentum spread of the electron wave packet at the tunnel exit

TL;DR

This study investigates the longitudinal momentum spread of electrons at the tunnel exit during strong-field ionization of Helium, combining experiments and semi-classical modeling to estimate this fundamental quantum property.

Contribution

It introduces a combined experimental and theoretical approach to quantify the longitudinal momentum spread at the tunnel exit in strong-field ionization.

Findings

Momentum distribution explained by longitudinal momentum spread

Estimate of the momentum spread at tunnel exit

Semi-classical model aligns with experimental data

Abstract

We present an ellipticity resolved study of momentum distributions arising from strong-field ionization of Helium at constant intensity. The influence of the ion potential on the departing electron is considered within a semi-classical model consisting of an initial tunneling step and subsequent classical propagation. We find that the momentum distribution can be explained by the presence of a longitudinal momentum spread of the electron at the exit from the tunnel. Our combined experimental and theoretical study provides an estimate of this momentum spread.