Double photoelectron emission from He atoms by intense laser pulses with a wavelength of 394.5 nm is computed for intensities of $3.5–9.2\times {10}^{14}\text{W}/{\text{cm}}^2$. 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 ${\text{He}}^{2+}/{\text{He}}^{+}$ ratios, and a modulation of joint energy spectra agree well with a recent experiment [K. Henrichs et al., Phys. Rev. A 98, 043405 (2018)] if one admits an increase in experimental intensities by a factor of $\sim 2$. We find that Freeman resonances enhance back-to-back 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 recollisions.

• Received 20 December 2019
• Accepted 19 May 2020

DOI:https://doi.org/10.1103/PhysRevA.101.063407