Spectrum and Energy Levels of Triply-Ionized Niobium (Nb IV)

Abstract

The spectrum of triply-ionized niobium Nb IV was observed from 300 Å to 4100 Å with sliding spark discharges on 10.7-m normal- and grazing-incidence spectrographs. The existing analysis of this spectrum [Meinders, E. et al., Physica Scripta 25, 527 (1982).] was extended to include the 5s2, 5p2, 5s5d, 5s4f, 5s6s, 4d6d, 4d7s, 4d5f, 4d6f and 4d5g configurations, which are practically complete. A few levels of 4d7p and a few missing levels of the already known 4d4f configuration were also located. One level of the 4d6p configuration was revised. There are now a total of 840 lines classified as transitions between 185 energy levels. Of these, 546 lines and 107 levels are new. From the optimized energy level values, Ritz-type wavelengths with uncertainties varying from about 0.0005 Å to 0.003 Å were 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 parameters were used to calculate oscillator strengths for all classified lines. An improved value for the ionization energy was obtained from the 4dns(n = 4–6), 4dnf(n = 4–6), and 4d5g configurations. The adopted value is 303350 ± 180 cm-1 (37.611 ± 0.022 eV).

Spectrum and energy levels of quadruply-ionized molybdenum (Mo V)

“…A recent ab inito calculation of this level by Pan and Beck [15] predicts 5s 2 1 S 0 to lie at 196 717 cm −1 . The agreement here is not as good as was obtained by these authors [16] for Zr III, where the calculated value of 48 712 cm −1 compared to the experimental value [7] of 48 507 cm −1 , and for Nb IV, where the calculated value of 116 826 cm −1 compared to the experimental value [8] of 116 921.51 cm −1 .…”

“…The present work was begun to locate the 4d5g configuration in Mo V. In both Zr III [7] and Nb IV [8], this configuration was found to make strong transitions to 4d4f, and since spectra of Mo were already available in our laboratory, it was likely that extension of the 4d4f-4d5g transitions to Mo V would be relatively straightforward. Although this goal was accomplished, it proved to be less than straightforward.…”

“…The values range from 1 to 900 000. The system that we use to obtain this extensive scale of intensities is described in detail in our paper on Nb IV [8]. For the present set, no attempt was made to account for variation in spectrograph or plate emulsion response.…”

“…Although this transition would normally be prohibited as a two-electron jump, the admixture of other odd states allows the line to be observed. As in Zr III [7] and Nb IV [8], the 5s4f 1 F 3 level is observed well below its predicted position; it was not included in our least-squares fit.…”

Heavy metal enrichment in the intermediate He-sdOB pulsator Feige 46

“…This is not reliable enough for an abundance measurement, but an upper limit of V/H = −5.4 can be estimated as many V lines are too strong at this abundance. We searched for niobium using Nb iv oscillator strengths provided by Tauheed & Reader (2005). Several unidentified weak lines in the GHRS spectrum (e.g., Nb iv λλ1445.…”