The [formula omitted] interaction in CO +: Deperturbation analyses of B– A and A– X bands of 12C 16O +, 13C 16O + and 14C 16O +

Abstract

The 1–0, 6–0 and 6–1 bands of the A 2 Π i → X 2 Σ + system of 13C 16O + and the 2–0 and 2–1 bands of the A 2 Π i → X 2 Σ + system of 14C 16O + have been recorded at high resolution for the first time. The 0–2 and 5–0 bands of the A → X system of 12C 16O + have also been recorded at higher resolution than in previous work. The spectra were excited in an air-cooled hollow cathode discharge and photographed using a 2-m plane grating spectrograph. The spectral resolution and the Doppler-broadened line widths are both ∼0.12 cm −1, and the experimental measurement precision of resolved lines is ∼0.02 cm −1. The measured line positions, sometimes in combination with literature data on the B 2 Σ + → A 2 Π i transition, have been employed in deperturbation analyses of level crossings in the near-degenerate A(0)∼ X(10) and A(5)∼ X(14) interactions in 12C 16O +, the A(1)∼ X(11) and A(6)∼ X(15) interactions in 13C 16O +, and the A(2)∼ X(12) interaction in 14C 16O +. No radial dependence of the electronic perturbation matrix elements H SO( r) and H RE( r) could be detected over the narrow range of r-centroids (1.477–1.501 Å), and the mean values of these parameters are H SO = −49.06(15) cm −1 and H RE = 0.211(2). Using iteratively improved RKR potentials and FC-overlap integrals, the mean H SO and H RE were employed in least-squares analyses of A → X literature data involving A( υ) levels of the three isotopologues that are affected by interactions with one or two distant X( υ∗) levels. The fitted parameters of the A 2 Π i state ( B υ , A υ , A Dυ , p υ , q υ ) exhibit υ-dependences that are much smoother than those employing perturbed parameters determined in previous investigations. In addition, a significant electronic isotope effect has been characterized. The separations T e( A)– T e( X) of the minima of the A and X states of 13C 16O + and 14C 16O + are less than that of 12C 16O + by 0.39 and 0.73 cm −1, respectively. Although Born–Oppenheimer breakdown of this magnitude is surprising, it is similar to that found for the B 2 Σ + state of CO +.