New atomic data calculations in the Yb I isoelectronic sequence (Ta IV - Pt IX) with relevance for nuclear fusion diagnostics

All elements from tantalum to platinum will be produced in Tokamaks through neutron-induced transmutation of the tungsten of which the divertor walls are composed. Therefore, ionic impurities of all possible charge states should appear in the fusion plasma, contributing to power loss, which does not make it easy to achieve self-maintained fusion reactions. However, the radiation that is emitted by these impurities will be useful for plasma diagnosis (impurity influx, temperature, and density). The identification of the spectral lines in experiments and knowledge of the radiative data for these ions are thus of great interest in this field. This work focuses on calculations of atomic structure, electric dipole transition probabilities, and oscillator strengths for isoelectronic elements of Yb I from tantalum to platinum. A new set of electric dipole transitions from Ta IV to Pt IX are determined and listed using two independent methods: the pseudo-relativistic Hartree–Fock method including core-polarization effects (HFR+CPOL), and the fully relativistic Multiconfiguration Dirac–Hartree–Fock (MCDHF) approach. The results from both methods are compared in order to assess the uncertainty and quality of the new data.