Rotational analysis of the A2Π u → X2Π g second negative band system of 16O 2+

Abstract

Twenty five bands of the A 2Π u → X 2Π g system of 16O 2 + with 0 ≤ v′ ≤ 8 and 2 ≤ v″ ≤ 11 have been photographed at high resolution. The measured positions of the assigned lines have been fitted by least-squares to obtain reliable molecular constants for all the observed levels. The Λ-type doubling effect has been attributed for the first time to the separate contributions of the A 2Π u and X 2Π g states. Unpublished data of Colbourn and Douglas for eight bands with 11 ≤ v′ ≤ 15 and v″ = 0, 1 have been reexamined, and fitted with the same effective 2Π Hamiltonian as that used for the new data. Merged constants based on all the available data are reported, and used to obtain RKR potentials for the A 2Π u and X 2Π g states. Λ-Doubling in the X 2Π g ground state can be understood in terms of an interaction principally with the B 2Σ g − state. Most of the constants for the higher levels of the A 2Π u state show anomalous behavior, which is discussed in terms of a perturbation with a previously unobserved, shallow-bound 2Σ u + state.