Excitation energies, term designations, and $g$ factors of Th, ${\mathrm{Th}}^{+}$, and ${\mathrm{Th}}^{2+}$ are determined using a relativistic hybrid configuration-interaction (CI) plus all-order approach that combines configuration-interaction and linearized coupled-cluster methods. The results are compared with other theoretical and experimental values where available. We find some vanishing $g$ factors, similar to those known in lanthanide spectra. Reduced matrix elements, oscillator strengths, transition rates, and lifetimes are determined for ${\mathrm{Th}}^{2+}$. To estimate the uncertainties of our results, we compare our values with the available experimental lifetimes for higher $5f7p{}^3{G}_4$, $7s7p{}^3{P}_0$, $7s7p{}^3{P}_1$, and $6d7p{}^3{F}_4$ levels of ${\mathrm{Th}}^{2+}$. These calculations provide a benchmark test of the CI plus all-order method for heavy systems with several valence electrons and yield recommended values for transition rates and lifetimes of ${\mathrm{Th}}^{2+}$.

• Received 13 August 2014

DOI:https://doi.org/10.1103/PhysRevA.90.032512