Relativistic configuration interaction (RCI) calculations predict that the ${4d}^7{5s}^{2}2J=9,$ 7, 5 and 3 ${}^{4}F$ levels of ${\mathrm{Ru}}^{-}$ are all bound with binding energies 1.076, 0.905, 0.795, and 0.725 eV, respectively. Using laser photodetachment threshold spectroscopy, the binding energies of the $2J=9$ and $2J=7$ levels are measured to be 1.04638(25) and 0.8653(10) eV, respectively, in good agreement with the calculated values. Hyperfine structure constants for all levels and magnetic dipole decay rates have also been calculated, and a systematic study of the important role of quadruple excitations is presented.

• Received 5 August 1998

DOI:https://doi.org/10.1103/PhysRevA.59.1896