European Conference on Trapped Ions (ECTI)

Radium-225 (nuclear spin 1/2) is a particularly appealing candidate for optical clocks and testing fundamental symmetries due to its accessible electronic structure and heavy, octupole deformed nucleus. We demonstrated the first laser cooling of short-lived ${}^{224}$Ra${}^{+}$ (3.6 day half-life) and ${}^{225}$Ra${}^{+}$ (15 day half-life) ions which are loaded into linear Paul traps by a two-step photoionization process. We observed the $7s{}^2$S${}_{1/2}\to 7d{}^2$D${}_{5/2}$ clock transition in ${}^{224}$Ra${}^{+}$ and ${}^{225}$Ra${}^{+}$. This work was done with an effusive oven source based on the decay of longer-lived thorium atoms, which is expected to provide a useful supply of radium atoms over several thorium half-lives. We will measure the absolute transition frequencies of the electronic transitions needed for laser cooling and operating an optical clock with both short-lived isotopes. In parallel efforts, we are measuring the hyperfine structure of ${}^{225}$Ra${}^{+}$ and developing an orthotropic oven to produce a more efficient radium source. In following work we will produce and trap radium molecules which have enhanced sensitivity to tests of fundamental symmetries.