Spectroscopic analysis of M- and N-intrashell transitions in Co-like to Na-like Yb ions

Abstract

The M-intrashell spectra from Co-like Yb43+ through Na-like Yb59+ ions produced in an electron beam ion trap (EBIT) at the National Institute of Standards and Technology have been studied in the extreme ultraviolet (EUV) range. A few N-intrashell transitions for Co-like Yb43+ and Fe-like Yb44+ are also reported. The EUV radiation was observed with a flat-field grazing incidence spectrometer in the wavelength region of about 7.5 nm to 26.2 nm. The electron beam energies were varied between 3.6 keV and 18 keV to produce the ionization stages of interest. The line identifications were based on the large-scale simulations of the EBIT plasma emission using the non-Maxwellian collisional-radiative code NOMAD. A total of 76 previously unobserved spectral lines corresponding to electric-dipole and magnetic-dipole transitions in the above mentioned ions were identified and discussed. In particular, our accurate wavelength of 24.3855 ± 0.0005 nm for a magnetic-dipole (M1) transition in the ground configuration of Co-like ion presents a solid benchmark for comparisons with the most advanced theories of atomic structure.