Impact-parameter dependence of inner-shell ionization cross sections induced by protons and He ions in the energy range 0.4--2.0 MeV/u

The impact-parameter dependence of the K-shell ionization cross section has been measured for protons and 3He ions incident on thin-foil targets of Ti, Ni, and Cu at selected energies in the region from 0.4 to 2.0 MeV/u. Comparison is made of these experimentally determined values with the results of a recently developed theoretical model in which the electron binding energy and initial-state wave function are allowed to respond in a time-dependent fashion to the field of the projectile as a function of its position along a hyperbolic Coulomb trajectory. Generally good agreement between the theoretical and experimental values is obtained. A comparison between the results of this theoretical model and two other published theoretical results and with experimental data for 0.5-MeV p in Cu is also shown. Remarkably close agreement is seen, particularly between the predictions of the rather disparate theoretical models. Measurements for a single system, 2.0-MeV p in Sm, involving ionization from the L shell, are also reported