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 405-875 nm are assigned. Our results will facilitate the future studies of absorption and emission spectra of OsO.