Spectrum and energy levels of singly ionized rubidium (Rb ii)

Abstract

The spectrum of Rb ii has been observed in a pulsed radio-frequency discharge with the NBS 10.7-m normal-incidence vacuum spectrograph, the NBS 10.7 m Eagle spectrograph in air, and the NBS 3.34 m plane-grating spectrograph in air. The observations cover the regions 1489–2661 A and 4380–10 081 A. The wavelengths of the strong resonance lines in the 530–741 A region were accurately measured in the 3rd and 4th orders with a sliding-spark discharge. Analysis of the spectrum has provided the positions of the previously missing levels of the 4p5 4d, 4f, and 6d configurations. The energy-level system has been extended to include the complete 4p5 5f, 5g, 6f, and 6g configurations, most of the levels of the 4p5 6p, 7f, 7g, 8s, and 9s configurations, and parts of the 4p5 7d, 8d, 8f, 8g, 9d, and 9f configurations. 600 lines are classified as transitions between 165 levels. Most of the observed configurations have been theoretically interpreted. The energy parameters determined from least-squares fits to the observed levels are compared with Hartree–Fock calculations. The ionization energy, derived from the 4p5nf 3/2[9/2]5, n = 4–7, and 4p5ng 3/2[11/2]6, n = 5–8, series, is 220 105.0 ± 0.5 cm−1 (27.2898 ± 0.0001 eV).