A new 4Σ − a4Π electronic transition of ScC in the near infra-red

Abstract

A new 4Σ − a4Πi electronic transition of ScC with (0,0) band near 12,700 cm−1 has been discovered using laser-induced fluorescence, following the reaction of laser-ablated scandium metal with acetylene or methane under supersonic jet-cooled conditions. The new bands are weak, since the a4Πi lower state is known from previous work to lie 160 cm−1 above the X2Π ground state; several spectra needed to be co-added in order to improve the signal-to-noise ratio. The rotational structure of the new transition is dense and heavily blended, but analysis has been possible for the strongest sub-bands of the (1,0) and (2,0) bands, respectively at 13,301 and 13,899 cm−1; extensive use was made of a band contour program for 4Σ − 4Π bands which listed the details of each line that it plotted. The bond length in the new 4Σ state is r0 = 1.964 Å, which is 0.01 Å longer than in the ground state; its vibrational frequency is 607 cm−1. There is no information in the spectrum giving the Kronig symmetry of the new state, though its electron configuration is probably (C 2pσ)1 (C 2pπ)2 (Sc 4sσ)1 (Sc 3dδ)1. Unexpectedly, the spin-spin interaction parameter, λ, in the new 4Σ state is negative, which suggests complicated interactions with nearby unseen electronic states.