Highly charged ions for atomic clocks and search for variation of the fine structure constant

Abstract

We review a number of highly charged ions which have optical transitions suitable for building extremely accurate atomic clocks. This includes ions from Hf¹²⁺ to U³⁴⁺, which have the 4f ¹² configuration of valence electrons, the Ir¹⁷⁺ ion, which has a hole in almost filled 4f subshell, the Ho¹⁴⁺, Cf¹⁵⁺, Es¹⁷⁺ and Es¹⁶⁺ ions. Clock transitions in most of these ions are sensitive to variation of the fine structure constant, $\alpha (\alpha = e^{2}/\hbar c)$. E.g., californium and einsteinium ions have largest known sensitivity to α-variation while holmium ion looks as the most suitable ion for experimental study. We study the spectra of the ions and their features relevant to the use as frequency standards.

Proceedings of the 6th International Conference on Trapped Charged Particles and Fundamental Physics (TCP 2014), Takamatsu, Japan, 1-5 December 2014.