High-resolution photoelectron spectroscopy of cryogenically cooled SiC−

We report high-resolution photoelectron spectroscopy of SiC- anions using a cryogenic ion trap combined with the slow-electron velocity-map imaging method. Photodetachment transitions to the neutral SiC ground state X 3Π and excited states (a 1Σ+, b 1Π) were observed, revealing the fine structure of the X 3Π band. A long-lived excited state (A 3Π) of SiC- was observed at 3380(101) cm-1 above the anionic ground state. The electron affinity (EA) was determined as EA(SiC) = 19 327(15) cm-1 or 2.396(2) eV. The spectroscopic constants of the ground state (X' 2Σ+) of SiC- were derived as ωe = 1016(21) cm-1 and ωexe = 5.20(22) cm-1.