X-ray spectra of F-like, O-like, and N-like barium from an electron-beam ion trap

An electron-beam ion trap has been used to study the spectra of highly ionized barium. Spectra of N-, O-, and F-like barium were produced by 10-keV electron-impact excitation and ionization and were observed using a von Hamos crystal spectrometer. Calibration lines were obtained by injection of Ti, V, Cr, and Zn into the trap and observation of H- and He-like transitions. A number of lines were identified for each of the ionization stages, and their energies were measured with a typical accuracy of about 150 ppm. These measurements have been compared to calculations using a multiconfigurational Dirac-Fock code. Agreement with the data is best for the F-like transitions, and diminishes for transitions in the more highly charged ions