Matrix Infrared Spectroscopy and a Theoretical Investigation of SUO and US2

Abstract

AbstractUS2 and SUO molecules have been prepared by laser ablation of the solid materials and reaction of the elements during condensation in solid argon, which give the same absorptions as earlier U atom reactions with sulfur vapor and sulfur dioxide. The antisymmetric stretching mode of US2 shifts from 438.7 cm–1 in solid argon to 442.3 cm–1 in solid neon, which shows that the same electronic state is trapped in both matrix environments. Density functional calculations find a bent (3B2) ground state for the US2 molecule, and CASSCF/CASPT2 calculations reveal a multiconfigurational mixture of (5fφ)1(5fδ)1‐type states, whereas the most stable state for UO2 is a linear structure of the (5fφ)(7s) type. The bent triplet ground state SUO molecule exhibits similar multireference character with the U–O stretching mode at 857.1 cm–1 in solid argon. The linear SUO molecule computed at the CASPT2 level is only 2 kcal/mol above the bent structure. A detailed analysis of the bonding in US2 and SUO is provided and compared to the better known UO2 molecule.