Production of highly charged low-velocity recoil ions by heavy-ion bombardment of rare-gas targets

The author has measured charge-state ($q$) spectra of recoil ions generated in single collisions of 25-45-MeV chlorine ions with targets of helium, neon, and argon. A high-efficiency time-of-flight spectrometer was used to identify the charge-to-mass ratio of the slowly moving recoils. Recoil $q$ up to + 8 (neon) and + 11 (argon) were observed. Cross sections for recoil production were measured as a function of projectile energy and incident charge state. The energy dependence of the cross sections is quite weak, while the recoil-$q$ dependences show clear shell effects in argon. For the lower-$q$ recoils, the cross sections are reasonably well described by the model of Olson, which treats the target electrons as moving independently. For higher $q$, a model based on energy deposition by the projectile with the target electrons, followed by statistically weighted electron emission, gives a better description of the data.