Projectile Angular Dependence of the Ratio of Double to Single Ionization Produced by Fast Protons in Collision with Helium

Abstract
We suggest an explanation for the structure, observed by Giese and Horsdal, in the projectile angular dependence of the ratio of double to single ionization produced by fast protons in collision with helium. We postulate that two incoherent mechanisms, a first that produces slow electrons and a second that produces fast electrons, combine to give the effect.