title: Intense-field double ionization of helium: identifying the mechanism
abstract: We present quantum mechanical calculations of the electron and ion momentum distributions following double ionization of a one-dimensional helium atom by ultrashort laser pulses (780 nm) at various intensities. The two-electron momentum distributions exhibit a clear transition from nonsequential to sequential double ionization. We provide strong evidence that rescattering is responsible for nonsequential ionization by calculating the momentum spectrum of the He2+ recoil ions-which we find in excellent agreement with recent experiments-and by analyzing the electronic center-of-mass motion via Wigner transforms.
authors.affiliation: Institut fur Physikalische Chemie, Am Hubland, 97074 Wurzburg, Germany and Institut fur Theoretische Physik, Am Hubland, 97074 Wurzburg, Germany.
authors.initials: M
authors.lastname: Lein
authors.initials: EK
authors.lastname: Gross
authors.initials: V
authors.lastname: Engel