Measurement and identification of EUV spectra from highly charged Yb in an electron beam ion trap

Extreme ultraviolet (EUV) spectra of Rb-like Yb$^{33+}$ through Na-like Yb$^{59+}$ ions were produced and accurately measured in an electron beam ion trap at National Institute of Standards and Technology. The EUV radiation was observed with a flat-field grazing incidence spectrometer in the wavelength region of 2 nm to 26 nm. The electron beam energies were varied between 1.6 keV and 8.6 keV to distinguish between different N- and M-shell ions. More than 100 new spectral lines due to $\Delta n$=0 electric-dipole and magnetic-dipole transitions were unambiguously identified using large-scale collisional-radiative (CR) simulations of non-Maxwellian EBIT plasma with the code NOMAD. The CR model included nearly 74,000 levels from about 30 ions of Yb which allowed us to reach a comprehensive description of level population kinetics. Also the Na-like D$_1$ 3s$_{1/2}$--3p$_{1/2}$ and D$_2$ 3s$_{1/2}$--3p$_{3/2}$ lines were measured at the electron beam energy of 18 keV thereby providing a test of relativistic and quantumelectrodynamic effects on atomic structure of highly-charged ions. Detailed comparisons between measurements and simulations will be presented.