Singlet States of ScF Below 23 000 cm−1: X1Σ+, A1Δ, B1Π, C1Σ+, D1Π, and E1Δ

Abstract Laser-induced fluorescence, chemiluminescence, and thermal emission of ScF have been analyzed in the visible and near-infrared regions with high-resolution Fourier transform spectrometry techniques. Spectra of several transitions involving singlet and triplet electronic states have been recorded. In the present article spectroscopic results are given for a number of unperturbed levels in the six lowest singlet states, v = 0-5, 9-13, 15 in X 1 Σ + , v = 0, 1, 2, 5 in A 1 Δ = 0-5 in B 1 Π, v = 0 in C 1 Σ + and E 1 Δ,and v = 0, 1, 5 in D 1 Π. A consistent set of molecular constants is derived from an overall treatment of about 4100 wavenumbers of lines in 45 bands which enables the observed wavenumbers to be reproduced to within 0.006 cm −1 , i.e., to about the experimental accuracy. Analysis of the B 1 Π − X 1 Σ + system confirms theoretical predictions that the accepted vibrational numbering in B 1 Π must be increased by two. Justification is provided from calculations of Franck-Condon factors which are in agreement with the observed band intensities. Moreover, interactions between B 1 Π and c 3 Σ + (O−) levels are recognized and appear responsible for (i) the large Λ-doubling in B 1 Π and its rapid evolution with v , and (ii) a hyperfine structure effect observed as a broadening of the Q lines.