Transitions 4p-5d, 6d and 4p-6s, 7s in Zr VI and Nb VII

Zirconium and niobium spectra were recorded on the 5m grazing incidence spectrograph from 125AA to 440AA. All the eight 6s levels are found in both the spectra. Other levels determined were four 7s, twenty 5d and eleven 6d in Zr VI, and six 7s, twelve 5d and thirteen 6d in Nb VII. The analyses are based on 52 classified lines of Zr and 45 of Nb. It is suggested from isoelectronic comparisons that the designation of the 6s 2 P 3/2 and 4 P 3/2 levels of Rb III should be interchanged. The authors evaluate the ionization potential 4p 5 2 P 3/2 -4p 4 3 P 2 .