The First infrared spectra and quasirelativistic DFT studies of the US, US(2), and US(3) molecules.

Laser-ablated U atoms react with discharged sulfur vapor in excess argon to form the US, US(2), and US(3) molecules, which are identified from matrix infrared spectra using sulfur isotopic substitution. Vibrational frequencies from quasirelativistic DFT calculations support these assignments and provide an insight into the bonding and structure. Unlike linear UO(2), US(2) is bent because of more favorable U(6d)-S(3p) overlap, and US(2) has a 118 +/- 5 degrees (experimental based on isotopic shift) or 121 degrees (calculated (3)B(2) ground state, B3LYP) S-U-S bond angle.