Charge-changing collisions of channeled oxygen ions in gold

Oxygen ions (4–40MeV) with various charge states have been used to study the effects of channeling upon emerging charge-state distributions and to determine the effect of channeling upon the charge-changing cross sections involved. At energies above 20 MeV, no true equilibrium is observed even for pathlength of 0.6 μm in Au channels. Instead we find quasi-equilibrium for charge states up to 6 + and strongly pathlength-dependent charge functions for 7 + and 8 + injection. The data are interpreted in terms of interaction with loosely bound outer electrons in Au.