Analysis of the Spectrum of Seven-Times-Ionized Molybdenum (Mo viii) and Isoelectronic Comparison of the Spectra Y v—Mo viii

The spectrum of Mo viii has been observed in a sliding-spark discharge with a 5-m grazing-incidence spectrograph. The analysis has yielded nearly all levels of the 4p44d configuration that can combine with the 4p5 2P ground term. Six of the eight levels of the 4p45s configuration given previously by Charles and by Chaghtai were confirmed. New values were found for the remaining two. The 4s24p44d+4s24p45s+4s4p6 level structure has been theoretically interpreted, with configuration-interaction effects included. The 4s4p6²S12 level was found to have a 21% 4s24p4(1D)4d2S character and the 4s24p4(¹D)4d²S12 level a 19% 4s4p6 2S character. The energy parameters determined by a least-squares fit to the observed level values are compared with Hartree–Fock (HF) calculations. The ionization energy is estimated to be 144.0 ± 1.0 eV. Isoelectronic comparisons for the level positions in Y v, Zr vi, Nb vii, and Mo v are given graphically. The ratios of the fitted energy parameters to the HF values are compared for these ions.