Double ionization of helium by electron impact in the impulsive regime

Experimental and theoretical fully differential cross sections were considered for double ionization of helium by 2-keV electron impact. The measurements were performed employing the reaction microscope which allows to detect simultaneously a large part of the final-state momentum space. Data were obtained for a noncoplanar geometry where one electron is emitted 45°C above and the second electron 45°C below the scattering plane.