Ionization and excitation of hydrogen molecules by fast proton impact

The ratio of ionization-excitation to single ionization of hydrogen molecules caused by fast proton impact was measured over a wide velocity range (upsilon = 6-24 au) using the coincidence time-of-flight technique. This ratio, similar to 2%, is independent of the collision velocity at high velocities. It differs from the ratio of total H+ to H-2(+) production mostly due to a large contribution from the dissociation of the electronic ground state of the molecular ion. The dissociation fraction of H-2(+)(1s sigma) was measured and compares well with our calculations using the Franck-Condon approximation.