Electronic Structure and Bonding of US, SUO, and US₂

Anion photoelectron spectra of US^- and US₂^- were recorded using the third (355 nm) and fourth (266 nm) harmonics of an Nd:YAG laser, which yielded vertical detachment energies (VDEs) of 1.71 and 2.02 eV, respectively. The experimental results are supported by extensive relativistic ab initio calculations, primarily at the coupled cluster level of theory, with systematic sequences of correlation consistent basis sets. Calculations include the closely related SUO and SUO^- molecules, as well as the oxide congeners UO/UO^- and UO₂/UO₂^- which are well-known experimentally and provide benchmark systems for the sulfide calculations. Adiabatic electron detachment energies (ADEs) are computed for UO^-, UO₂^-, US^-, SUO^-, and US₂^- using the Feller-Peterson-Dixon (FPD) composite approach. In addition, ADEs are determined for UO^- and US^- using a spinor-based coupled cluster approach where spin-orbit coupling is included at the orbital level. VDEs are derived from the ab initio results from Franck-Condon simulations of the photoelectron spectra.