Extensive theoretical study on electronically excited states and predissociation mechanisms of sulfur monoxide including spin–orbit coupling

The potential energy curves of the 69 Ω states generated from the 24 Λ–S states of sulfur monoxide are calculated for the first time using the internally contracted multireference configuration interaction method with the Davidson correction and the entirely uncontracted aug‐cc‐pV5Z basis set. Spin–orbit coupling is taken into account by the state interaction approach with the full Breit–Pauli Hamiltonian. Very good agreement is achieved between our computed spectroscopic properties and the available experimental data. The transition properties of the B3Σ−–X3Σ− and (4)1–X0+ transitions are predicted, and our computed Franck–Condon factors and radiative lifetimes match the experimental results very well. The predissociation mechanisms are investigated, and various new predissociation channels are located. We present a new interpretation on the breaking‐off of the rotational levels of the B3Σ− lower vibrational states observed in experiment, and propose that the predissociation is induced by the Coriolis coupling between the B3Σ− rovibrational levels and the A3Π state. Our calculations indicate that, at ν′ = 9, the B3Σ− state predissociates via the C3Π state; around ν′ = 14, three spin‐orbit‐induced predissociation pathways via (1)5Σ+, (2)5Π, and e1Π would be open; around ν′ = 17, the pathways via (2)1Σ+, (2)3Σ+ and (2)5Σ+ would contribute. These satisfactorily explain the experimental results about the diffuseness of the B3Σ− bands. Furthermore, various predissociation pathways of the C′3Π state are predicted, through which the C′3Π state could predissociate rapidly. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011