Theoretical study on predissociation of B3Σu- of sulfur dimer.

Abstract A high level ab initio study on electronic states of sulfur dimer S2 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 B3Σu− state. The variation of line width of B3Σu−- X3Σg− transitions with vibrational quantum number v' of the B3Σu− are determined from Fermi golden rule calculations. Our study indicate that the predissociation of the B3Σu− 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.