Analyses of the ScO− and ScO2− photoelectron spectra

We have optimized geometries for various electronic states of both neutral and anionic ScO and ScO2 using density functional theory (DFT) and coupled cluster theory. Adiabatic and vertical separation energies have been computed using both DFT and coupled cluster theory. For the ScO− anion the 1Σ+ state is predicted to lie lower than the 3Δ state by 1.48 eV. In fact, the anion 3Δ state is higher in energy than the 2Σ+ neutral ground state. This contradicts the assignment of the ScO− ground state made by Wu and Wang, in their recent report of photoelectron spectroscopy experiments. The CCSD(T) adiabatic electron affinity for the ground state of ScO is 1.30 eV, while the vertical detachment energy is 1.33 eV. This compares favorably with the experimental value of 1.35 eV. For ScO2 the 2B2 ground state with a CCSD(T) bond angle of 140.5° is lower in energy than the 2A1 state with a bond angle of 48.4° by 1.13 eV. The anion minima include two 1A1 states, with the CCSD(T) global minimum corresponding to 140.9° ...

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