Competing processes for electron capture to continuum in relativistic ion-atom collisions

Abstract

The relative importance of the two mechanisms for the capture of a target electron by a fast, heavy projectile, radiative ionization (RI) and Coulomb capture to continuum (ECC), is studied in the vicinity of the forward peak. For both processes a consistent relativistic description, based on the impulse approximation, is provided. It is found that the differential cross-sections scale with the projectile charge and exhibit a common velocity dependence. As a result, RI starts to dominate over ECC near the same impact energy (∼11 MeV/amu) for arbitrary bare projectiles colliding with hydrogen. For electrons from the inner shells of heavier targets this energy increases, however, which is confirmed by a coincidence experiment on 90 MeV/amu U 88+ +N 2.