Multiple ionization of heavy targets by H+ and hydrogen impact

We have investigated multiple ionization of noble gases by proton and hydro gen impact at low and intermediate projectile energies; 50, 120 and 210 keV . The recoil-ion-charge-state-selected yields were measured in coincidence with electrons emitted at 90 degrees with respect to the beam direction. Di fferential yields were obtained for recoil-ion charges up to five. For sing le ionization a comparison with previous data gives good agreement for the electron energy range of interest here. Significant differences were observ ed for the case of charged and neutral projectiles. Comparisons between mul tiple and single ionization were made. For the targets investigated, Kr, Ne , Ar, we observed a characteristic structure, which depends on projectile c harge and velocity. For proton impact, the ratio of multiply to singly char ged recoils presents a distinctive enhancement at an electron velocity clos e to that of the projectile. This structure disappears for H impact, probab ly due to the dominance of simultaneous ionization of target and projectile electrons.