Abstract
Restricted‐spin coupled‐cluster single‐double plus perturbative triple excitation {RCCSD(T)} potential energy functions (PEFs) of the $ \tilde X $^2^B~2~ state of ScO~2~ and the $ \tilde X $^1^A~1~ state of ScO~2~^−^ were computed, employing the augmented correlation‐consistent polarized‐weighted core‐valence quadruple‐zeta (aug‐cc‐pwCVQZ) basis set for Sc and augmented correlation‐consistent polarized valence quadruple‐zeta (aug‐cc‐pVQZ) basis set for O, and with the outer core Sc 3s^2^3p^6^ electrons being explicitly correlated. Franck‐Condon factors, which include allowance for Duschinsky rotation and anharmonicity, were calculated using the computed RCCSD(T) PEFs, and were used to simulate the first photodetachment band of ScO~2~^−^. The simulated spectrum matches well with the corresponding experimental 355 nm 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 ScO~2~ gave adiabatic relative electronic energies (T~e~'s) of, and vertical excitation energies (T~v~'s) to, the $ \tilde A $^2^A~1~, $ \tilde B $^2^B~1~, and $ \tilde C $^2^A~2~ states of ScO~2~ (from the $ \tilde X $^2^B~2~ state of ScO~2~), as well as electron affinities (EAs) and vertical detachment energies (VDEs) to these neutral states from the $ \tilde X $^1^A~1~ state of ScO~2~^−^. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009