Resonant and nonresonant indirect electron-impact single ionization of beryllium-like carbon ions via K-shell excitation

A joint experimental and theoretical study of electron-impact single ionization of beryllium-like carbon ions (C²⁺) is presented. Absolute cross sections are measured for electron-ion collision energies from the ionization onset up to 500 eV by using the animated crossed-beams method. Signatures of resonant and nonresonant indirect ionization processes involving the excitation of a K-shell electron were observed in the measured total ionization cross section. The present state-of-the-art distorted-wave–approximation calculations reproduce the experimentally observed structures well. Small remaining deviations of the theoretical data from the experimental findings show that the accurate description of many-body processes in highly correlated atomic systems remains a challenge. (paper)