Accurate calculation of electron affinity for S₃

The accurate equilibrium structures of S₃ and S₃^- are determined by the coupled-cluster method with single, double excitation and perturbative triple excitation (CCSD(T)) with basis sets of aug-cc-pV(n+d)Z (n=T, Q, 5, or 6), complete basis set extrapolation functions with two-parameters and three-parameters, together with considering the contributions due to the core-valence electron correlation, scalar relativistic effects, spin-orbit coupling, and zero-point vibrational corrections. Our calculations show that both the neutral S₃ and anion S₃^- have open forms with C_2v symmetry. On the basis of the stable geometries, the adiabatic electron affinity of S₃ is determined to be 19041(11) cm^-1, which is in excellent agreement with the experimental data (19059(7) cm^-1). The dependence of geometries and electron affinity on the computation level and physical corrections is discussed. The present computational results are helpful to the experimental molecular spectroscopy and bonding of S₃.