SINGLE CAPTURE AND TRANSFER IONIZATION IN COLLISIONS OF CL-Q+ PROJECTILE IONS INCIDENT ON HELIUM

The Kansas State University linac has been used to measure the ratio o f the cross sections for the processes of transfer ionization (TI) and single capture (SC) for 2 MeV/amu Cl-q+ where q = 7, 9, 13, 14, and 1 5 projectile ions incident on a helium target. The ratio was determine d using a helium gas jet target by measuring coincidences between proj ectile-ion and recoil-ion final charge states. The sigma(TI)/sigma(SC) for Cl-q+ were compared to measurements of bare F9+ and hydrogenlike F8+ and O7+ taken at the same velocity. The ratios deviate from a q(2) scaling which is predicted in the perturbative regime. This deviation is attributed to screening by the projectile electrons for low q = 7 and 9, and to the collision being non-perturbative for high q. A possi ble saturation effect in the ratio was observed for q similar to 14.