Identification of EUV Spectral Lines from Highly Charged Zr, Nb, Mo, and Pr Ions Using an Electron Beam Ion Trap

The extreme ultraviolet (EUV) spectra of highly charged Zr, Mo, Nb, and Pr ions were measured using the electron beam ion trap (EBIT) at the National Institute of Standards and Technology. Emissions in the 2–20 nm wavelength range were captured with a flat-field grazing-incidence EUV spectrometer. By varying the electron beam energy between 2.5 keV and 11.8 keV, different ionization stages were selectively produced. Identification of spectral lines was supported by the NOMAD collisional-radiative model, which accounts for the non-Maxwellian nature of the EBIT plasma. A range of new spectral lines was identified for Li-like through Ne-like ions for Zr, Nb, and Mo ions, and Na-like through Ar-like Pr ions. These transitions correspond to both electric-dipole and magnetic-dipole transitions.