Momentum Distribution of Near-Zero-Energy Photoelectrons in the Strong-Field Tunneling Ionization in the Long Wavelength Limit

TL;DR

This study explores the momentum distribution of near-zero-energy photoelectrons in strong-field tunneling ionization of Argon at long wavelengths, revealing unexpected accumulations and structures explained by Coulomb effects and classical trajectories.

Contribution

It provides new insights into the momentum distribution features of photoelectrons at long wavelengths, supported by semiclassical simulations and experimental agreement.

Findings

Accumulation of near-zero-energy photoelectrons observed.

V-like structure at larger transverse momenta identified.

Coulomb attraction crucial for distribution features.

Abstract

We investigate the ionization dynamics of Argon atoms irradiated by an ultrashort intense laser of a wavelength up to 3100 nm, addressing the momentum distribution of the photoelectrons with near-zero-energy. We find a surprising accumulation in the momentum distribution corresponding to meV energy and a \textquotedblleft V"-like structure at the slightly larger transverse momenta. Semiclassical simulations indicate the crucial role of the Coulomb attraction between the escaping electron and the remaining ion at extremely large distance. Tracing back classical trajectories, we find the tunneling electrons born in a certain window of the field phase and transverse velocity are responsible for the striking accumulation. Our theoretical results are consistent with recent meV-resolved high-precision measurements.