Spectra of the W VIII isoelectronic sequence: II. Ta VII

Abstract

Tantalum spectra excited in vacuum spark sources with different set-ups 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 in the Meudon Observatory. In the region below 350 Å, a 3 m grazing incidence spectrograph with a 3600 l mm−1 grating was used in the Institute of Spectroscopy in Troitsk. A total of 237 lines in the region of 191–354 Å were identified as transitions from the interacting excited even configurations 4f125s25p6(5d + 6s) + 4f135s25p5(5d + 6s) + 4f145s25p4(5d + 6s) to the low-lying odd configurations 4f135s25p6 and 4f145s25p5. Fine structure splittings and relative positions of the odd terms were established, and 126 levels of the excited even configurations were found.