Theoretical study on predissociation of BΣ of sulfur dimer.

A high level ab initio study on electronic states of sulfur dimer S is carried out by utilizing multi-reference configuration interaction plus Davidson correction (MRCI+Q) method. The modification to the electronic structures caused by spin-orbit coupling (SOC) effect is taken into consideration by the state-interacting method with the full Breit-Pauli Hamiltonian. The potential energy curves (PECs) of 19 Λ-S states and 52 Ω states generated from the Λ-S states are calculated. With the aid of calculated SOC matrix elements and the PECs of the Ω states, we discuss the predissociaiton of the BΣ state. The variation of line width of BΣ- XΣ transitions with vibrational quantum number v' of the BΣ are determined from Fermi golden rule calculations. Our study indicate that the predissociation of the BΣ state is induced by the strong spin-orbit coupling with different electronic excited states, resulting in the abnormal dependence of the dissociation rate on vibrational states.