Ab initio investigations of the unimolecular decay of CS+2 for internal energies lower than 10 eV

One-dimensional potential energy curves of the lowest doublet and quartet states of CS+2 and their mutual spin-orbit interactions have been calculated using the complete active space self-consistent field and internal contracted multi-reference configuration interaction methods. Between the A2Πu and the C2Σ+g states, four doublet satellite states (two 2Πu, one 2Πg and one 2Φu) in addition to the valence B2Σ+u state are found. The two 2Πu states have been already observed in the photoelectron spectra where they were associated with a long vibronic progression. Several quartet states have been also located in the 3-10 eV internal energy range. The avoided crossing regions and the conical intersections for the doublets and the quartets are located. The predissociation mechanisms of the doublet states of CS+2 leading to the first dissociation limit (S+(4Su) + CS(X1Σ+)) are also discussed. They are found to involve vibronic and/or spin-orbit interactions between the doublet and the quartet states