Transitions among the first three low-lying states in the highly charged $\mathrm{W}^{13+}, \mathrm{Ir}^{16+}$, and $\mathrm{Pt}^{17+}$ ions are found to be strongly forbidden with wavelengths in the optical regime. By determining their energy levels, lifetimes, and other spectroscopic properties that are decisive quantities for estimating dominant systematics due to stray electromagnetic interactions in an experiment, we demonstrate that it can be possible to measure frequencies of the lowest forbidden transitions below a ${10}^{-19}$ precision level in the above ions, and hence, they seem to be suitable for frequency standards. We employ a sophisticated relativistic coupled cluster method to carry out calculations of these properties of the above states involving $4f$- and $5s$-core orbitals. We also found, by estimating their relativistic sensitivity coefficients, that these clock transitions can be highly sensitive to the tiny drift in the fine-structure constant ${\alpha }_e$. Consequently, a clock based on one of these ions, particularly $\mathrm{Pt}^{17+}$, could be used for corroborating the hypothesis of temporal and spatial variation in ${\alpha }_e$.

• Received 22 June 2016
• Revised 26 July 2016

DOI:https://doi.org/10.1103/PhysRevA.94.032504