Electron capture and ionization of 33-TeV Pb ions in gas targets -: art. no. 032711

We have measured the total cross sections for electron capture by bare Pb82+ ions and for the ionization of hydrogenlike Pb81+(1s) ions at 158 GeV/A, gamma =168, in Ar, Kr, and Xe gas targets. At this energy, the total capture cross sections are dominated by electron capture from pair production. The capture measurements are compared with the results of several theoretical calculations and with similar measurements made with solid targets. The Pb81+(1s) ionization cross sections obtained, which are substantially lower than those measured in solids, agree well with recent calculations that predict saturation at high energies from target screening effects.