Quasi-simultaneous double ionization of helium in super-intense high-frequency laser pulses

In super-intense laser pulses beyond the tunneling regime, non-sequential double ionization is known to be of little significance, especially due to the laser-induced Lorentz force. We show that, for such intense fields, electron-electron repulsion does still play a crucial role in the case of quasi-instantaneous double ionization with long electron-electron interaction times at short separations. For this purpose the time-dependent quantum dynamics and the angular ionization yields are investigated for a model helium atom beyond the dipole approximation