Spectra of the W VIII isoelectronic sequence: I. Hf VI

Hafnium spectra excited in vacuum spark sources of different setups and electric circuits were recorded on two high-resolution vacuum spectrographs. For the wavelength region 300–500 Å, a 10 m normal incidence spectrograph with a 3600 l mm⁻¹ grating was used at the Meudon Observatory. In the region below 350 Å, a 3 m grazing incidence spectrograph with a 3600 l mm⁻¹ grating was used at the Institute of Spectroscopy in Troitsk. A total of 189 lines in the region 193–474 Å were identified as transitions from the interacting excited even configurations 4f¹²5s²5p⁶5d + 4f¹²5s²5p⁶6d + 4f¹³5s²5p⁵(5d + 6s) + 4f¹⁴5s²5p⁴(5d + 6s) + 4f¹⁴5s5p⁶ to the low-lying odd configurations 4f¹³5s²5p⁶ and 4f¹⁴5s²5p⁵. Fine structure splittings and relative positions of the odd terms were established, and 142 levels of the excited even configurations were found. (paper)