Nonsequential double ionization of argon atom below the recollision threshold

Abstract

Nonsequential double ionization (NSDI) of Ar atom below the recollision threshold is investigated using the three-dimensional classical ensembles. The calculated results reveal a dominance of events for electron emission into opposite hemispheres, a clear minimum of the correlated electron-electron momentum distributions at the origin and a single peak structure of the Ar2+ ions longitudinal momentum spectra near zero momentum. The momentum spectra of the Ar2+ ions agree with the experimental results 101 053001 (2008)] quantitatively. Trajectory back analyses show that the microscopic physical mechanisms of Ar NSDI are distinct for different intensities of the laser. When laser intensity equal to 0.7×1014 W/cm2, one recollision dominates the process of the recollision. However,the domination convert to multiple recollisions as the laser intensity decreases to 0.4×1014 W/cm2. In addition, the Coulomb attraction between the ion and electron plays an important role in microscopic dynamics of the electron in the process of Ar NSDI and eventually influences the final-state correlated electron-electron momentum distributions strongly.