Spectrum and energy levels of five-times ionized tantalum (Ta vi)

Abstract

The spectrum of Ta vi produced with a sliding-spark discharge was photographed in the region of ~200–2000 Å utilizing grazing-incidence and normal-incidence spectrographs. A system of seventy excited energy levels was deduced from 228 spectral lines. These arise from excitations out of both the 4f and 5p closed shells of the 4f¹⁴5s²5p⁶ ground configuration, giving the observed configurations 4f¹³nl with nl = 5d, 6s, 6p, 6d, 7s and 5p⁵nl with nl = 5d, 6s, 6p. Radial integrals were fitted for all of these configurations. A value of 785 130 ± 400 cm⁻¹ for the ionization energy was derived. A graph of lowest excited levels of 4f¹³5d and 5p⁵5d from Lu iv to Re viii predicts the crossing of these configurations after W vii.