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 CS2+ 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 A(2)Pi(u) and the C(2)Sigma(g)(+) states, four doublet satellite states (two (2)Pi(u), one (2)Pi(g) and one (2)Phi(u)) in addition to the valence B(2)Sigma(u)(+) state are found. The two (2)Pi(u) 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 CS2+ leading to the first dissociation limit (S+(S-4(u)) + CS(X(1)Sigma(+))) are also discussed. They are found to involve vibronic and/or spin-orbit interactions between the doublet and the quartet states.