Theoretical prediction of the state–state correlation among doublet state AlSO isomers

The geometries and the harmonic vibrational frequencies for several AlSO doublet state isomers have been predicted at density functional theory (DFT) levels with a 6-311+G∗ basis set. Results have indicated that there are five stable doublet states (two cyclic, two linear and one bent structure) and only four of them keep S–O bond linkage, but the most stable one has a broken O–S linear structure and should be referred to as the ground-state (2Σ) isomer. The state–state energy separations are determined and the properties of these low-lying state isomers are also characterized. The state–state correlation and the isomerization mechanism are predicted by searching the transition states.