SPECTRUM AND ENERGY-LEVELS OF DOUBLY-IONIZED ZIRCONIUM (ZRIII)

The spectrum of doubly-ionized zirconium ZrIII, was observed from 630 Angstrom to 4610 Angstrom with sliding spark discharges on the 10.7-m normal-incidence vacuum spectrograph at the National Institute of Stan dards and Technology. The spectral analysis of C. C. Kiess, J. Res. Na tl. Bur. Std (U.S.) 56, 167 (1956), was considerably revised and exten ded. Experimental energies were obtained for almost all levels of the 4d(2), 4d5s, 5s(2), 4d5p, 5s5p, 4d5d, 4d6s, 4d6p, 4d4f, 5p(2), 5s6s, 5 s5d, 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 be tween 139 energy levels. From the optimized energy level values, a sys tem of Ritz-type wavelengths with uncertainties varying from about 0.0 05 Angstrom to 0.003 Angstrom was determined. The observed configurati ons were theoretically interpreted by means of Hartree-Fock calculatio ns and least-squares fits of the energy parameters to the observed lev els. The fitted energy parameters were used to calculate oscillator st rengths and transition probabilities for all classified lines. An impr oved value of the ionization energy was obtained from the 4d4f, 4d5f a nd 4d5g configurations. The adopted value is 186 880 +/- 30 cm(-1) (23 .170 +/- 0.004 eV).