Inner Shell Studies in Transition Metal Negative Ions: d-shell Photoexcitation and Detachment

Results of the first inner-shell photoexcitation and detachment studies conducted on the transition metal negative ions will be presented. The experiments were conducted on Ru$^{-}$, Ni$^{-}$, Pd$^{-}$, and Pt$^{-}$ near the ns, np shells (n=3 for Ni, 4 for Ru and Pd, 5 for Pt) , and 4f shell (in Pt). All ions show significant probabilities for multi-electron ejection in the detachment and decay mechanisms, with a total of up to 4 electrons removed. Excitation of a p-electron into the nearly-filled d-shell (in Ru$^{-}$, Ni$^{-}$, and Pt$^{-})$ results in strong shape resonances, and excitation of a 4f-electron gives rise to conspicuous Feshbach resonances in Pt$^{-}$. In contrast, no resonances are observed in Pd$^{-}$, owing to its completely filled valence 4d shell, in spite of being in the same group as Ni and Pt.