Projectile charge dependence of ionization and fragmentation of CO in fast collisions

Abstract

Single and multiple ionization cross sections of CO have been measured as a function of the projectile charge. The experiment was carried out at fixed collision energies of 1 MeV using the coincidence time-of-flight technique. The cross sections increase rapidly for small q and more slowly for large q. The branching ratios of all the transient molecular ions and the kinetic energy distribution of the dissociating transient exhibit similar projectile charge dependence. These observed trends are explained quite satisfactorily using a simple model based on perturbation theory and the independent electron approximation. The model predicts that the average value of the projectile - electron interaction strength in collisions resulting in target ionization varies quickly for small q and more slowly for large q.