One and two electron processes in fast collisions between protons and hydrogen molecules

Abstract

The ratio of double to single ionization of hydrogen molecules caused by fast proton impact was measured over a wide velocity range ( v = 6–24 a.u.) using the coincidence time-of-flight technique. This ratio, ∼ 0.13% at high velocities, is about a factor of 2 smaller than the same ratio for the He target. This difference is due mainly to the larger single ionization cross section for hydrogen molecules, i.e. σ +(H 2) ∼ 2 σ +(He). The double ionization cross section, on the other hand, is similar for both He and H 2. Furthermore, the ratio of double to single ionization of the hydrogen molecule by proton impact is smaller than the one caused by electron impact at the same velocity in a similar way as for the helium target.