Predicting the energies of Cf17+ for an optical clock

TL;DR

This paper provides accurate theoretical predictions of the energy levels and clock transition of Cf17+ ions, crucial for developing optical clocks using highly charged ions, by employing advanced relativistic coupled-cluster calculations.

Contribution

It introduces a comprehensive relativistic coupled-cluster approach including nonlinear and triple excitations for precise energy predictions of Cf17+ ions.

Findings

Reliable prediction of the 5f_5/2 - 6p_1/2 clock transition energy.

Core-valence correlations and iterative triples significantly affect energy calculations.

Assessment of quantum-electrodynamic and basis-set effects enhances accuracy.

Abstract

Highly charged ions (HCIs) combine compact electronic structure with strong relativistic effects, offering both robustness against external perturbations and enhanced sensitivity to variations of the fine-structure constant. Recent advances in sympathetic cooling and trapping enable precision measurements of highly charged ions; however, fully exploiting their potential requires accurate theoretical predictions. In particular, reliable calculations of clock wavelengths are essential for experimentally locating HCI clock transitions. Here, we treat Cf17+ as a univalent ion and perform calculations within the relativistic coupled-cluster framework, iteratively including nonlinear single-double contributions and valence and core triple excitations. We also assess quantum-electrodynamic corrections and basis-set and partial-wave truncation effects. Our results establish the impact of different correlation contributions on the low-lying energy spectrum and provide a quantitatively reliable prediction of the 5f_5/2 - 6p_1/2 clock transition, highlighting the critical role of core-valence correlations and iterative triples for precision spectroscopy and optical clock development.