Multiple ionization in relativistic heavy-ion–atom collisions

We show that in relativistic heavy-ion collisions the independent-electron model can be used to predict cross sections for multiple inner-shell ionization in a single collision. Charge distributions of 430- and 955-MeV/amu U⁹⁰⁺, U⁸⁹⁺, U⁸³⁺, and U⁶⁸⁺ beams emerging from thin solid targets were used to obtain single- and multiple-electron stripping cross sections. The probabilities of stripping electrons from the K, L, or M shells were calculated using the semiclassical approximation and Dirac hydrogenic wave functions. The data generally agree with theory. An influence of the Auger effect is seen in U⁶⁸⁺ collisions.