Deep-core dielectronic-capture resonances in the electron-impact ionization of heavy atomic ions

Experimental measurements and theoretical calculations are carried out far the electron-impact ionization of Sm12+. The low energy region of the singl e ionization cross section for Sm12+ is found to be dominated by contributi ons from the indirect process of excitation autoionization. At about 1.0 ke V strong resonance features are found in the experimental crossed-beam meas urements performed in scan mode at high resolution. Theoretical calculation s confirm that the high energy experimental features are due to deep-core d ielectronic capture followed by sequential double Auger decay. The discover y of these unusual high energy resonances in single and multiple ionization opens the deter for future systematic studies of how heavy atomic ions wit h deep inner-shell vacancies achieve final stabilization.