On-line Excited-State Laser Spectroscopy of Trapped Short-Lived Ra${}^{+}$ Ions

As an important step towards an atomic parity violation experiment in one single trapped Ra${}^{+}$ ion, laser spectroscopy experiments were performed with on-line produced short-lived ${}^{212,213,214}$Ra${}^{+}$ ions. The isotope shift of the $6{}^2$D${}_{3\mathrm{/}2}$,-,$7{}^2$P${}_{1\mathrm{/}2}$ and $6{}^2$D${}_{3\mathrm{/}2}$,-,$7{}^2$P${}_{3\mathrm{/}2}$ transitions and the hyperfine structure constant of the $7{}^2$S${}_{1\mathrm{/}2}$ and $6{}^2$D${}_{3\mathrm{/}2}$ states in ${}^{213}$Ra${}^{+}$ were measured. These values provide a benchmark for the required atomic theory. A lower limit of $232(4)$ ms for the lifetime of the metastable $6{}^2$D${}_{5\mathrm{/}2}$ state was measured by optical shelving.