Calculations of transition rates in erbium-like ions Lu IV, Hf V and Ta VI using the Ab initio MCDHF-RCI and semi-empirical HFR methods

In the present paper, the radiative properties of three ions belonging to the erbium isoelectronic sequence, i.e. Lu IV, Hf V and Ta IV, are reported and the effect of configuration interaction on these properties are taken into account for the first time to our knowledge. These heavy elements with Z=71–73 are located near to tungsten (Z=74) in the Periodic Table and are of potential interest in controlled thermonuclear fusion. Indeed, they could be used in plasma-facing materials such as the divertors in tokamaks or/and could be generated by neutron-induced transmutations of divertor’s materials. In this work, two independent theoretical atomic structure computational approaches have been considered, i.e. the semi-empirical Hartree–Fock with relativistic corrections method (HFR) and the ab initio multiconfiguration Dirac–Hartree–Fock with subsequent relativistic configuration interaction method (MCDHF-RCI). The transition probabilities and the oscillator strengths have been calculated for 593, 820 and 1101 E1 transitions in Lu IV, Hf V and Ta VI respectively spanning the spectral range from UV to IR. Finally, this study also underlines the importance of core-valence correlations in these heavy atomic ions.