Analysis of recoil ion momentum in near threshold double ionization of helium by electron impact

An experiment on near threshold double ionization of helium impacted with 106 eV electron has been performed by using the newest developed reaction microscope. In this experiment the momenta of all products after double ionization of helium were measured and the five fold differential cross section was obtained for emitted electrons. The angular correlation between the emitted electrons, which equally shared the excess energy, was analyzed in the plane defined by the projectile and the first detected electron. The experimental result was compared with different theoretical calculations. It was found that DS6C model described the experimental reasonably. (authors)