The electronic spectrum of the CS+ molecular ion: rotational analysis and perturbation effects in the A2Πi–X2Σ+ transition

Abstract

A new emission spectrum in the red region (6000–8000 Å) has been recorded from a low pressure hot cathode discharge through carbon disulfide. This band system has been assigned to the A²Π_i–X²Σ⁺ transition of the CS⁺ molecular ion on the basis of the rotational analysis and comparison with other nine valence-electron molecules. Molecular constants have been obtained by direct least squares fits of the line frequencies to the difference of the eigenvalues of standard ²Π and ²Σ⁺ matrices.A local perturbation in the A²Π_i (ν = 5) state has been studied quantitatively. The position of the perturbing vibrational level in the X²Σ⁺ state has been determined within a few centimetre⁻¹. This study gave a consistent set of molecular constants for the ground state of CS⁺ and allowed a partial deperturbation treatment of the observed vibrational levels of the excited A²Π_i state.Numerous bands are also observed in the 4000 Å region. A discussion is given concerning the possible assignment of bands at 4059 and 4110 Å to the CS⁺B²Σ⁺–A²Π_i (0,0) transition.