Laser spectroscopy of trapped Th$^{3+}$ ions

We are applying the techniques of laser cooling and ion trapping to investigate the low lying nuclear isomeric state in $^{229}$Th. We will confine Th$^{3+}$ atoms in an RF trap [1] and sympathetically cool them with barium ions. The ions are produced by laser ablation from a thorium metal target by the third harmonic of a Q-switched YAG laser. Using mass-spectroscopic techniques we separate out the Th$^{3+}$ ions from the plume of ablation products. We once trapped we will observe fluorescence from the trapped ions using transitions at 984 nm and 690 nm. [1] Peik E. and Tamm Chr., \textit{Europhysics Letters}, \textbf{61} (2) (2003)