Adiabatic inner-shell ionization by light ions

For very slow collisions, the ionization cross section depends on the projectile kinematics in the combined field of the nucleus and atomic electrons, on the time evolution of the electron wave function, and on the recoil of the nucleus. First-order semiclassical cross sections in the united-atom limit were calculated for the Thomas-Fermi and Hartree-Fock screening potentials. The time evolution of the wave function was considered by the model of a perturbed harmonic oscillator and by a simplified atomic model involving only a few lowest states. Theoretical K-shell ionization cross sections were compared with the mean experimental data calculated for groups of atoms with neighboring atomic numbers. It was pointed out that the averaging process, also employing theoretical data, depends essentially on the projectile kinematics in the screened atomic field. Taking this into account, good agreement between mean experimental and theoretical cross sections was obtained.