Restricted-spin coupled-cluster single-double plus perturbative triple excitation {RCCSD(T)} potential energy functions (PEFs) of the (X) over bar B-2(2) state of ScO2 and the (X) over bar (1)A(1) state of ScO2- were computed, employing the augmented correlation-consistent polarized-weighted core-valence quadruple-zeta (aug-cc-pwCVQZ) basis set for Sc and core Sc 3s(2)3p(6) electrons being explicity correlated. Franck-Condon factors, which include allowance for Duschinksy rotation and anharmonicity, were calculated using the computed RCCSD(T) PEFs, and were used to simulate the first photodetachment spectrum of Wu and Wang, J Phys Chem A 1998, 102, 9129, confirming the assignment of the photodetachment spectrum and the reliability of the RCCSD(T) PEFs used. Further calculations on low-lying electronic states of ScO2 gave adiabatic relative electronic energies (T-c's) of, and vertical excitation energies (T-v's) to the (A) over bar (2)A(1), (B) over bar B-2(1), and (C) over bar (2)A(2) states of ScO2 (from the (X) over bar B-2(2)) state of ScO2), as well as electron affinities (EAs) and vertical detachment energies (VDEs) to these neutral states from the (X) over bar (1)A(1) state of ScO2-. (C) 2008 Wiley Periodicals, Inc.