Measurements of the L-shell x-ray emission of fluorinelike europium

Measurements of the L-shell x-ray emission of fluorinelike europium ions (Eu54+) were made under controlled laboratory conditions on the EBIT-I electron beam ion trap at Livermore using an x-ray calorimeter, extending such measurements to the middle of the rare earth elements. Comparing the calorimeter spectra with atomic data from the Flexible Atomic Code, we have identified and analyzed several prominent n = 3 → n = 2 transitions, including one two-electron, one-photon core changing transition and one electric quadrupole transition. We find that the measured energies are consistently up to several eV higher than predicted.