The (X ²∏_g) nsσ_g ^1,3∏_g Rydberg states of O₂: Spectra, structures and interactions

The results of a critical reexamination of previous experimental observations of the (X²∏_g) nsσ_g ^1,3∏_g Rydberg states of O₂ are employed to optimize a coupled-channel Schrödinger-equation (CSE) model describing rovibronic interactions among a number of ^1,3∏_g Rydberg and valence states. The results of calculations using this CSE model are compared with the experimental energy-level and predissociation linewidth data base. As a result of the optimization process, relevant potential-energy curves and Rydberg-valence, Rydberg-Rydberg, and valence-valence interactions are characterized for ^1,3∏_g states in the ∼6.5-9.5 eV region above the ground state of O₂. The precision of these characterizations and the interpretation of the experimental observations are found to be limited by the quality of the existing data, which exhibit a number of inconsistencies that cannot be reconciled without new, well-characterized experimental studies. In spite of these difficulties, the present CSE model, as currently parametrized, represents a significant improvement over previous work, enabling identification of a number of previously unassigned spectral features associated with perturbation of the 3sσ_g d ¹∏_g state by the ∥ ¹∏_g valence state and an anomalous J sensitivity in predissociation branching ratios for the d(v = 1) level. In addition, the electronic structure and predissociation of the nsσ_g states for n≥4 are found to be strongly influenced by nsσ_g -(n-1)dσ_g Rydberg-Rydberg interactions.