Spectra of the W VIII isoelectronic sequence: III. Re IX

Rhenium spectra excited in vacuum spark sources of different setups and electric circuits were recorded on two high resolution vacuum spectrographs: a 10 m normal incidence spectrograph with a 3600 l mm⁻¹ grating in the Meudon Observatory and a 3 m grazing incidence spectrograph with a 3600 l mm⁻¹ grating in the Institute of Spectroscopy in Troitsk. A total of 112 lines in the region 146–244 Å were identified as transitions from the interacting excited even configurations 4f¹²5s²5p⁶5d + 4f¹³5s²5p⁵(5d + 6s) + 4f¹⁴5s²5p⁴(5d + 6s) to the low-lying odd configurations 4f¹³5s²5p⁶ and 4f¹⁴5s²5p⁵. A change of the ground configuration from 4f¹³5s²5p⁶ to 4f¹⁴5s²5p⁵ in a comparison with the previous spectra of the isoelectronic sequence Hf VI–W VIII was observed. Fine structure splittings and relative positions of the odd terms were established, and 83 levels of the excited even configurations were found. (paper)