Energy structure and radiative parameter calculations in the Re-like Pt IV, Au V and Hg VI spectra and preliminary line identifications in Hg VI

Highlights: • Theoretical and experimental analysis of the Hg VI spectrum. • Transition probabilities, predicted energy levels and wavelengths. • The 5d⁷, 5d⁶6p and 5d⁶6s configuration studied for the first time. • Comparative study of three ions: Pt IV, Au V and Hg VI. • Uncertainty estimation for the transition rates. We performed extended ab-initio atomic structure calculations for Ir III-like Pt IV, Au V and Hg VI by using the pseudo-relativistic Hartree-Fock approach (HFR). These computations yielded theoretical energy levels and transition data for the electric dipole (E1) transitions. The results obtained in this study compare well with the available experimental data. More precisely, the good agreement of our theoretical calculations with experimental values for Pt IV and Au V allowed us to execute precise calculations for Hg VI by scaling the Slater parameters similar to Au V which is next to Hg VI in Re isoelectronic sequence. Most of our computed energy levels and radiative transition rates for Re-like Hg VI were not reported before. We provide accurate and comprehensive atomic data related to this ion that could be used by astrophysicists for interpretation of stellar spectra. On the basis of these calculations, preliminary identifications of 32 strong Hg VI lines were made in our experimental spectrograms.