Transitions between the $4f$-core-excited states in Ir$^{16+}$, Ir$^{17+}$, and Ir$^{18+}$ ions for clock applications

Understand

Iridium ions near $4f$-$5s$ level crossings are the leading candidates for a new type of atomic clocks with a high projected accuracy and a very high sensitivity to the temporal variation of the fine structure constant $\alpha$.

• To identify spectra of these ions in experiment accurate calculations of the spectra and electromagnetic transition probabilities should be performed.
• Properties of the $4f$-core-excited states in Ir$^{16+}$, Ir$^{17+}$, and Ir$^{18+}$ ions are evaluated using relativistic many-body perturbation theory and Hartree-Fock-Relativistic method (COWAN code).
• We evaluate excitation energies, wavelengths, oscillator strengths, and transition rates.