Extreme UV observation of 3–3 transitions of niobium in near neon-like charge states

Abstract The emission spectra of highly ionised niobium ions generated by beam-foil excitation in the range 7–21 nm show most 3–3 transitions belonging to the neon-like ions and neighbouring Na-, Mg- and F- sequences. Wavelengths have been determined in reference to Δ n =1 transitions between Rydberg states. Line identification have been made by comparison to extra- or interpolation of wavenumbers along isoelectronic sequences when data were available and to ab initio atomic structure calculations, using either a Cowan code or a fully relativistic parametric code for Ne- and F-sequences.