Measurements and identifications of extreme ultraviolet spectra of   highly-charged Sm and Er
  We report spectroscopic measurements of highly charged samarium and erbium performed at the National Institute of Standards and Technology (NIST) Electron Beam Ion Trap (EBIT). These measurements are in the extreme ultraviolet (EUV) range, and span electron beam energies from 0.98 keV to 3.00 keV. We observed 71 lines from Kr-like Sm$^{26+}$ to Ni-like Sm$^{34+}$, connecting 83 energy levels, and 64 lines from Rb-like Er$^{32+}$ to Ni-like Er$^{40+}$, connecting 78 energy levels. Of these lines, 64 in Sm and 60 in Er are new. Line identifications are performed using collisional-radiative modeling of the EBIT plasma. All spectral lines are assigned individual uncertainties, most in the $\sim$0.001 nm range. Energy levels are derived from the wavelength measurements. 
Y.A. Podpaly, J.D. Gillaspy, J. Reader, Yu. Ralchenko
physics.atom-ph