SUPPLEMENTARY MATERIAL

Table S1 Fitted bond lengths and spectroscopic constants of RhO and RhO− using Dunham potential to the seventh-order; Table S2 Spin-free ground and low-lying excited states of RhO at its corresponding anion geometry at the CASPT2 level; Table S3 Spin-free ground and low-lying excited states of RhO− at the CASPT2 level; Figure S1 potential energy curves of RhO− and RhO calculated at the CASPT2 level. Figure S2 Potential energy curves calculated at the CASPT2 level using state-average CASSCF wave functions as reference for RhO and RhO−.