Electron double-emission spectra for Helium atoms in intense 400 nm laser pulses

TL;DR

This study computationally investigates double photoelectron emission from helium atoms under intense 400 nm laser pulses, revealing emission patterns, resonance effects, and electron interactions that align with experimental observations.

Contribution

It provides detailed computational analysis of helium double-emission spectra, highlighting resonance effects and electron correlations not previously characterized.

Findings

Transition from back-to-back to side-by-side emission with increasing intensity

Resonance enhancements increase anti-correlated emission

Modulation of energy spectra indicates multiple recollisions

Abstract

Double photoelectron emission from He atoms by intense laser pulses with a wave length of $394.5\,nm$ is computed for intensities $3.5 - 9.2\times 10^{14}W/cm^2$. Joint momentum distributions confirm the characteristics seen in classical trajectory calculations. The pronounced transition from back-to-back to side-by-side emission with increasing intensity, the $He^{++}/He^+$ ratios, and a modulation of joint energy spectra agree well with a recent experiment [Henrichs et al., PRA 98, 43405 (2018)], if one admits an increase of experimental intensities by a factor $\sim 2$. We find that Freeman resonances enhance anti-correlated emission, we identify the signature of electron repulsion in joint angular distributions, and we interpret the modulation of joint energy spectra as a signature of multiple recollsions.