Double photo-electron momentum spectra of Helium at infrared wavelength

TL;DR

This paper presents ab initio calculations of double photo-electron spectra of Helium at various wavelengths, extending the tSurff method to full 3+3 dimensions and analyzing electron correlation effects.

Contribution

The study extends the time-dependent surface flux method to full 3+3 dimensions and provides detailed spectra and correlation analysis at infrared wavelengths.

Findings

Results agree with recent literature at short wavelengths.

Reproduces experimental ionization ratios at 780 nm up to high intensities.

Provides detailed two-electron energy and angular distributions.

Abstract

Double photo-electron momentum spectra of the Helium atom are calculated \textit{ab initio} at extreme ultra-violet and near infrared wavelengths. At short wavelengths two-photon double ionization yields, two-electron energy spectra, and triply differential cross sections agree with results from recent literature. At the near infrared wavelength of $780\,nm$ the experimental single-to-double ionization ratio is reproduced up to intensities of $4\times 10^{14}W/cm^2$, and two-electron energy spectra and joint angular distributions are presented. The time-dependent surface flux (tSurff) approach is extended to full 3+3 spatial dimensions and systematic error control is demonstrated. We analyze our differential spectra in terms of an experimentally accessible quantitative measure of correlation.