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 captur e cross sections are dominated by electron capture from pair production. Th e capture measurements are compared with the results of several theoretical calculations and with similar measurements made with solid targets. The Pb 81+(1s) ionization cross sections obtained, which are substantially lower t han those measured in solids, agree well with recent calculations that pred ict saturation at high energies from target screening effects.