Ionisation of H-, He- and Li-like 1 GeV Ni ions in solid carbon targets

Abstract

Data for the electron loss from 1 GeV H-, He- and Li-like Ni ions incident on thin solid carbon targets have been obtained. The targets were sufficiently thin to achieve single-collision conditions and hence permit the determination of the ionisation cross sections. Despite the high velocity ( beta approximately 0.2) of the H-like Ni ions the collision regime is such that neither the Bohr theory based on an impact parameter formalism nor the Born approximation, even to second order, are appropriate for treating the ionisation process. The cross sections measured for electron loss were found to be significantly lower than these theoretical estimates. The single-electron ionisation cross sections for the Li-like Ni ions showed a marked increase over those for the H-like or He-like ions consistent with a strong electron binding energy dependence.