Energy structure investigations in triply ionized mercury: Hg IV

We report energy level structure of triply ionized mercury (Hg IV). The spectrum was recorded on a 3-m normal incidence vacuum spectrograph in the wavelength region 300 - 20 00 degrees A, using a triggered spark source at the spectroscopy laboratory, St. Francis Xavier University, Antigonish in Canada. Wavelength measurement and the corresponding uncertainties caused by calibration procedures are carefully analyzed. Based on the analysis of original measurements, the energy levels are optimized, which resulted in an improved set of energy level values. A complete disentanglement of the origin of these energy levels may well be impossible; therefore, new configurations have been extended in our theoretical calculations using Cowan's pseudo-relativistic Hartree-Fock code with superposition of interacting configurations. All preceding results were confirmed, and the 5d(8)(6d + 7s) mixed configurations have been newly established with the aid of experimental data supported by theoretical calculations. Along with the optimized energy eigenvalues, the observed and Ritz wavelengths, transition rates, and eigenvector compositions of Hg IV are also given. The energy level values were optimized using a computer code LOPT. (C) 2021 Published by Elsevier Ltd.