A new emission produced from sulfur monochloride in a helium afterglow: S+2(A2Πu-X2Πg,r)

A theoretical investigation of the S2+ cation in the gas phase

The potential energy curves (PECs) of 18 lowest energy Λ-S states of the S2+ cation have been calculated using the complete active space self-consistent field method followed by the internally contracted multireference configuration interaction approach with the Davidson modification. When spin−orbit coupling is computed using the Breit−Pauli Hamiltonian with the cc-pCVTZ basis set, the 18 Λ-S states split into 56 Ω components. To improve the quality of the PECs, core−valence correlation and scalar relativistic corrections are included. All PECs are extrapolated to the complete basis set limit. Based on the PECs obtained by the icMRCI+CV+DK+Q/(CBS-56) calculations, the spectroscopic parameters of 17 Λ-S bound states and 50 Ω bound states are obtained. The transitions (including the Franck−Condon factors and radiative lifetimes) from two low-lying states to the ground state are calculated for several low vibrational levels. Analyses show that the spectroscopic parameters reported here can be expected to be reliably predicted.

Coupled cluster study of the energetic properties of S2x (x=0,+1,1)

Ab initio electronic structure calculations are reported for S2, and its ions S2+ and S2-. Geometric parameters are calculated using the singles and doubles coupled cluster method, including a perturbational correction for connected triple excitation, together with systematic sequences of correlation consistent basis sets extrapolated to the complete basis set (CBS) limit. Energetic and structural properties of S2 and the S2 cation and anion are reported. The heat of formation of S2 (3Sigmag-) at 0 K in the gas phase is predicted to be 29.8 kcal/mol from the average of CBS two extrapolation procedures, less than the experimental heat of formation of S2 of 30.66+/-0.07 kcal/mol. The 0 K adiabatic ionization potential and electron affinity are predicted to be 9.37 and 1.68 eV, respectively.