A unified treatment of 2Π–2Π Rydberg–valence state interactions in NO

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Abstract
Generalized quantum defect theory is used to study the 2Π–2Π Rydberg–valence state perturbations in the NO molecule. The work is a generalization of the two‐step quantum defect treatment used previously by Giusti‐Suzor and Jungen for the calculation of competing preionization and predissociation processes in NO. The existing high‐resolution spectroscopic data, mainly from Miescher and co‐workers, are used to extract a set of quantum defect parameters relating to the pπ Rydberg channel associated with the NO+ X 1Σ+ state, and to determine potential energy curves for the B 2Π and L 2Π states as well as Rydberg–valence interaction parameters. Based on these parameters, the observed term values including rotational and spin–orbit effects are reproduced with a mean deviation of 4 cm−1 for all the 2Π levels from 45 500 to 71 600 cm−1 (i.e., to within 200 cm−1 of the dissociation limit). The fit is better than that previously obtained by Gallusser and Dressler in a vibronic perturbation approach, particularly for the levels near the dissociation limit. The set of parameters is used for the calculation of competing electronic predissociation and vibrational preionization of Rydberg levels lying above the dissociation limit and the v+=0 ionization limit. The resonance widths and energies measured recently by Anezaki et al. by a MPI double resonance technique are better reproduced by the present calculation than in the previous work of Giusti‐Suzor and Jungen.