Spectrum and energy levels of doubly-ionized zirconium (Zr III)

Abstract

The spectrum of doubly-ionized zirconium Zr III, was observed from 630 Å to 4610 Å with sliding spark discharges on the 10.7-m normal-incidence vacuum spectrograph at the National Institute of Standards and Technology. The spectral analysis of C C Kiess (1956 J. Res. Natl. Bur. Std. (US) 56 167), was considerably revised and extended. Experimental energies were obtained for almost all levels of the 4d2, 4d5s, 5s2, 4d5p, 5s5p, 4d5d, 4d6s, 4d6p, 4d4f, 5p2, 5s6s, 5s5d, 4d5f, 4d5g and 5s4f configurations as well as for a few levels of 4d7p and 4d6f. A total of 482 lines were classified as transitions between 139 energy levels. From the optimized energy level values, a system of Ritz-type wavelengths with uncertainties varying from about 0.005 Å to 0.003 Å was determined. The observed configurations were theoretically interpreted by means of Hartree-Fock calculations and least-squares fits of the energy parameters to the observed levels. The fitted energy parameters were used to calculate oscillator strengths and transition probabilities for all classified lines. An improved value of the ionization energy was obtained from the 4d4f, 4d5f and 4d5g configurations. The adopted value is 186 880 ± 30 cm−1 (23.170 ± 0.004 eV).