Electron-impact ionization of Sm12+ ions: Resonances far beyond threshold - art. no. 062705

Unusual resonance features at high energies were recently discovered in the experimental crossed-beams measurements of the electron-impact ionization of Sm12+. Theoretical calculation were able to confirm that they Lire due t o deep-core excitation with capture into dielectronic states followed by se quential double Auger decay [K. Aichele et al.. Phys. Rev. Lett. 86, 620 (2 001)]. In this paper additional experimental results are presented. showing more resonances in the sing le-ionization cross section. Detailed level-to -level calculations of dielectronic capture provide a clear identification of these resonances, as produced by a 3d-4f excitation vith capture to diff erent nl orbitals followed by sequential emission of mo electrons. By using configuration-average distorted-wave calculations, we estimate the branchi ng ratios for single and double ionization by considering the possible auto ionization paths leading to resonant contributions to excitation, single io nization, and double ionization.