An ab initio study on some low-lying singlet and triplet states of and quartet states of SbO2

RCCSD(T) calculations on low-lying singlet and triplet states of SbO 2 + , employing basis sets of up to aug-cc-pV5Z quality, give a linear X ∼ 1 Σ g + state with computed adiabatic and vertical ionization energies of 10.11 and 10.65 eV, respectively. CASSCF/MRCI calculations on low-lying quartet states of SbO2 give the lowest quartet state, an a ˜ 4 A 1 state, with a Te of 53.7 kcal mol−1 (2.33 eV). Reliable ionization energies to the a ˜ 3 B 2 and b ˜ 3 A 2 states of SbO 2 + and vertical excitation energies from the X ∼ 2 A 1 state of SbO2 to low-lying doublet and quartet states have also been computed to assist future spectroscopic identification of SbO2.