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The radiative decay of excited states of the negative ion of rhodium, Rh^-, has been investigated experimentally and theoretically. The experiments were conducted at the Double ElectroStatic Ion Ring Experiment (DESIREE) facility at Stockholm University using selective photodetachment from a stored ion beam to monitor the time evolution of the excited state populations. The lifetimes of the Rh^- ³F₃ and ³F₂ fine structure levels were measured to be 3. 2 (6) ~s and 21 (4) ~s, respectively. An additional, previously unreported, higher-lying bound state of mixed ¹D₂+³P₂+ (4d⁹5s) ¹D₂+³F₂ composition was observed and found to have a lifetime of 10. 9 (8) s. The binding energy of this state was determined to be in the interval 0. 1584 (2) eV < Eb < 0. 2669 (2) eV, using laser photodetachment threshold (LPT) spectroscopy. An autodetaching state with a lifetime of 480 (10) microseconds was also observed. Theoretical calculations of the excited-state compositions, energies, and magnetic-dipole transition lifetimes were performed using the multiconfiguration Dirac-Hartree-Fock and relativistic configuration interaction methods. The calculated lifetimes of the ³F₃ and ³F₂ fine structure levels are in excellent agreement with the measured values. The present study should provide valuable insights into electron correlation effects in negative ions and forbidden radiative transitions.
Karls et al. (Tue,) studied this question.