Inner-shell photodetachment from Se$^{-}$*

The photodetachment spectrum of Se$^{-}$ has been investigated using the merged ion-photon beam photodetachment technique. Se$^{-}$ ions were produced in a Cs sputtered negative ion source (SNICS II) while the photons were produced by the undulator on the Advanced Light Source Ion-Photon Beamline 10.0.1. Positive Se ions formed by multiple detachment were detected as a function of photon energy. Correlations in short-lived negative ion resonances formed by completely filling the valence 4$p$ shell in Se$^{-}$ by photoexcitation of 3$d $electrons lead to three resonance structures above 50 eV. The 3$p $threshold is observed above 156 eV and multielectron detachment resonance structure is observed near the 3$s$ photodetachment threshold above 220 eV. Comparisons to inner-shell detachment from S$^{-}$ and Te$^{-}$ are discussed.