Extensive Theoretical Study on Electronically Excited States and Predissociation Mechanisms of Sulfur Monoxide Including Spin-Orbit Coupling

The potential energy curves of the 69 Omega states generated from the 24 Lambda 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 B-3 Sigma(-) -X-3 Sigma(-) 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 B-3 Sigma(-) lower vibrational states observed in experiment, and propose that the predissociation is induced by the Coriolis coupling between the B-3 Sigma(-) rovibrational levels and the A(3)Pi state. Our calculations indicate that, at nu' = 9, the B-3 Sigma(-) state predissociates via the C-3 Pi state; around nu' = 14, three spin-orbit-induced predissociation pathways via (1)(5)Sigma(+), (2)(5)Pi, and e(1)Pi would be open; around nu' = 17, the pathways via (2)(1)Sigma(+), (2)(3)Sigma(+) and (2)(5)Sigma(+) would contribute. These satisfactorily explain the experimental results about the diffuseness of the B-3 Sigma(-) bands. Furthermore, various predissociation pathways of the C'(3) P state are predicted, through which the C'(3)Pi state could predissociate rapidly. (C) 2011 Wiley Periodicals, Inc. J Comput Chem 32: 1577-1588, 201