Frozen Core Approximation and Nuclear Screening Effects in Single Electron Capture Collisions

Differential cross sections (DCS) for single electron capture from helium by heavy ion impact are calculated using a frozen core 3-body model and an active electron 4-body model within the first Born approximation. DCS are presented for H+, He2+, Li3+, and C6+ projectiles with velocities of 1 MeV/amu and 10 MeV/amu. In general, the DCS from the two models are found to differ by about one to two orders of magnitude with the active electron 4-body model showing better agreement with experiment. Comparison of the models reveals two possible sources of the magnitude difference: the inactive electron's change of state and the projectile-target Coulomb interaction used in the different models. Detailed analysis indicates that the uncaptured electron's change of state can safely be neglected in the frozen core approximation, but that care must be used in modeling the projectile-target interaction.