Low-lying electronic states of osmium monoxide OsO

Abstract

The ground state of osmium monoxide (OsO) has long been controversial. In this paper, the low-lying Λ–S and Ω electronic states of OsO have been comprehensively studied by the high-precision multi-reference calculations. The ground state of OsO is unexpectedly the closed-shell 1Σ+ state with a double bond instead of the previously reported 3Φ or 5Σ+ state; after including the spin–orbit coupling effects, the ground state becomes 3Π2. With the help of the theoretical spectroscopic constants and transition dipole moments, the emission spectra in the region of 405 nm–875 nm are assigned. Our results will facilitate the future studies of absorption and emission spectra of OsO.