Laser-reduced fluorescence detection of carbon monoxide npσ (n = 5–8) triplet Rydberg states

Members of the npσ 3Σ+ (υ = 0) Rydberg series of the CO molecule in the range n = 5–8 have been detected and rotationally analysed using a three-step excitation scheme via a perturbed valence ‘doorway’ state. Starting from n = 6, l-uncoupling becomes evident. Molecular constants for a p-complex Hamiltonian have been obtained. Strong predissociation, growing with n, was found for all observed members of the series. The N-dependence of the linewidths is explained by the combined effects of l-uncoupling and a homogeneous perturbation of the npπ 3Σ+ states.