Double and single ionization of helium by high velocityN7+ions

Abstract
Beams of fully stripped nitrogen ions have been used to investigate the behavior of the double-to-single ionization cross-section ratio of helium in the 1030-MeV/amu velocity region. The measured ratio was found to remain nearly constant over this velocity range at a value of 0.01, which is about 4.5 times higher than the high-velocity limit established previously for q=1 projectiles.