A theoretical study on the gas phase reaction of La+ with CS2

The reaction of La+ with CS2 has been investigated at B3LYP and CCSD(T) levels of theory. The reaction mechanisms have been explored in detail on both triplet and singlet potential energy surfaces. The experimentally observed product LaS+ has been explained by the dissociation of the identified C-S bond insertion intermediate S-La-C-S+. The spin-forbidden reaction La+(3F) + CS2 → LaS+(1Σ ) + CS (1Σ) was found to be energetically much favorable than the spin-allowed reaction La+(3F) + CS2 → LaS+(3Σ) + CS (1Σ). According to the identified reaction mechanisms, the triplet-singlet surface crossing is suggested and the crossing region is approximately determined. The experimental result that the product LaS+ was observed at low-energy reaction condition has been rationalized.