Role of cascade and Auger effects in the enhanced population of the C3+(1s2s2p 4P) states following single-electron capture in C4+(1s2s 3S)-He collisions

The population of excited three-electron states in carbon ions after single-electron capture in 0.5-1.1 MeV/amu C4+(1s2s 3S)-He collisions is analyzed theoretically by combining different methods. While the two-center basis generator method is used to calculate capture amplitudes on the single-particle level, all-electron structure calculations for the relevant C3+ states and their radiative and Auger transition rates are performed on the multiconfiguration Dirac-Fock level. These data are then combined and fed into a set of classical rate equations for the decay dynamics. Total cross sections for the production of the 1s2s2p 4P, 1s2s2p 2P-, and 1s2s2p 2P+ states are calculated and their ratios compared with recent experimental data and previous calculations [D. Strohschein et al., Phys. Rev. A 77, 022706 (2008)]. It is found that the relative intensities of the 1s2s2p 4P states are considerably larger than expected on the basis of pure spin statistics. The Auger transitions, which were not included in the previous calculations, have a significant effect on the final results in that they reduce the 1s2s2p 2P intensities. Although our extended computations explain a significant part of the production of the 1s2s2p 4P states, the experimentally observed enhancement of these states is still considerably larger than the theoretical one.