Theoretical study on predissociation of B3Σu- of sulfur dimer

A high level ab initio study on electronic states of sulfur dimer S-2 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 Lambda-S states and 52 Omega states generated from the Lambda-S states are calculated. With the aid of calculated SOC matrix elements and the PECs of the omega states, we discuss the predissociaiton of the B-3 Sigma(-)(u)-state. The variation of line width of B-3 Sigma(u)-X-3 Sigma(g)- transitions with vibrational quantum number v' of the B-3 Sigma(-)(u) are determined from Fermi golden rule calculations. Our study indicate that the predissociation of the B-3 Sigma(-)(u) 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. (C) 2020 Elsevier B.V. All rights reserved.