Multiple ionization of argon in coincidence with projectile ions in 60-1120 MeV Siq+-Ar collisions

A projectile ion-recoil ion coincidence technique has been employed to stud y the,multiple ionization and the charge transfer processes in collisions o f 60-120 MeV Siq+ (q = 4-14) ions with neutral argon atoms. The relative co ntribution of different ionization channels, namely; direct ionization, ele ctron capture and electron loss leading to the production of slow moving mu ltiply charged argon recoil ions have been investigated. The data reported on the present collision system result from a direct measurement in the con sidered impact energy for the first time. The total ionization cross-sectio ns for the recoil ions are shown to scale as q(1.7)/E-p(0.5), where E-p is the energy in MeV of the projectile and q.its charge state. The recoil frac tions for the cases of total- and direct ionizations are found to decrease with increasing recoil charge state j. The total ionization fractions of th e recoils are seen to depend on q and to show the presence of a 'shell-effe ct' of the target. Further, the fractions are found to vary as 1/j(2) upto j = 8+. The average recoil charge state (j) increases slowly with q and wit h the number of lost or captured electrons from or into the projectile resp ectively. The projectile charge changing cross-sections sigma(qq') are foun d to decrease with increasing q for loss ionization and to increase with q for direct- and capture ionization processes respectively. The physics behi nd various scaling rules that are found to follow our data for different io nization processes is reviewed and discussed.