Electronic bands of scandium monocarbide, ScC, in the region 14 140-16 000 cm⁻¹

Scandium monocarbide molecules, ScC, have been prepared by the reaction of 532 nm laser-ablated Sc metal with acetylene or methane under supersonic jet-cooled conditions. Electronic spectra of Sc¹²C and Sc¹³C have been recorded in the region 14 140-16 000 cm⁻¹ using laser-induced fluorescence, and about 40 bands of each isotopomer have been analyzed rotationally. Wavelength resolved emission spectra have been obtained for many of them. The results show that Sc¹²C has a ²Π_i ground state, with a bond length of 1.952 Å. Its vibrational frequency and spin-orbit coupling constant are 648 cm⁻¹ and −39.47 cm⁻¹, respectively (631 cm⁻¹ and −39.32 cm⁻¹ in Sc¹³C). Lying 155.58 cm⁻¹ above the X²Π_3/2 level (154.72 cm⁻¹ in Sc¹³C) is a ⁴Π_5/2 level, the lowest spin-orbit component of a ⁴Π_i state. The excited states at higher energy are very complicated. Bands from both the doublet and quartet spin manifolds are present, and there are strong doublet-quartet interactions which induce many nominally-forbidden bands violating the selection rule ΔS = 0. Eight excited electronic states have been recognized, including four ⁴Δ states. These ⁴Δ states represent four of the five ⁴Δ states from the electron configurations (C 2pσ)² (C 2pπ)² (Sc 3dδ)¹ and (C 2pσ)¹ (C 2pπ)² (Sc 4sσ)¹ (Sc 3dδ)¹.