Extended analysis of the Ba XII spectrum in the EUV region

Abstract

The spectrum of the 11 times ionized barium (Ba XII) was extended and partly revised. The 4d 9 -(4d 8 5p + 4d 8 4f + 4p 5 4d 10 ) transition array was investigated in the 90-150 Å wavelength region. Twenty-nine out of thirty-two levels of the 4d 8 5p configuration reported by Sugar et al (1983 J. Opt. Soc. Am. 73 1077 and all four levels of the 4d 8 4f configuration reported by Gayasov and Joshi (1998 J. Phys. B: At. Mol. Opt. Phys. 31 L705) were confirmed. Twenty-eight new levels of the 4d 8 (5p + 4f ) and 4p 5 4d 10 configurations have been established. Eighty lines are now classified in the Ba XII spectrum, out of which thirty-seven lines are newly classified. Results of the analysis were supported by least-squares fitting of the determined energies. The semi-empirical energy parameters are consistent with Hartree-Fock (HF) evaluation of radial integrals in the Te VIII-Ba XII isoelectronic sequence.