Theoretical study of collision and collision-free radiative lifetimes of S₂(B³Σ_u^-(ν′ = 0 - 9))

We calculate multireference configuration-interaction wavefunctions and the potential-energy curves for the B³Σ_u^-and X³Σ_g^- states of the collision-free S₂ molecule and the T-shape collision complex S₂-He using cc-pVQZ basis sets. We obtain the transition dipole moments of the S₂(B³Σ_u^-→X³Σ_g^-) and the Franck-Condon factors between the vibrational levels of this two states. We evaluate the radiative lifetimes of S₂(B³Σ_u^-(′=0-9)) levels of the collision complex and the collision-free molecule and compare them with the experiments. The collision provides little change in the radiative lifetimes of S₂(B³Σ_u^-(′=0-9)) according to the previous calculations. We obtain excellent agreement between the theoretical results and the experiments. The data calculated are very useful in the study of the microwave-driven high-pressure sulfur lamp and an S₂ laser pumped by a transverse fast discharge.