Spectroscopic analysis of extreme-ultraviolet transitions in highly charged Nb ions

Extreme ultraviolet (EUV) spectra of highly charged Nb ions have been produced and confined in an electron beam ion trap at National Institute of Standards and Technology. A flat-field grazing incidence EUV spectrometer in the wavelength region of ≈ 2 - 17 nm was used to observe the EBIT radiation. The electron beam energies were varied between 4.5 keV and 8.1 keV to create the ionization stage of interest. Highly charged Ne, Xe and Ba ions were used to calibrate the EUV spectra. Several new electric-dipole and magnetic-dipole transitions from Le-like to Na-like Nb ions were identified and the line identification was aided by a collisional radiative non-Maxwellian code NOMAD.