Charge exchange and chemical reactions with trapped thorium ions

Most atomic nuclei have excitation energies ranging from keV to MeV. A unique exception is the $^{229}$Th nucleus, which has an excited state just several eV above the nuclear ground state.\footnote{B.~R.~Beck \textit{et al.}, \textit{Phys. Rev. Lett.} \textbf{98}, 142501 (2007).} Th$^{3+}$ provides a convenient level structure for laser cooling in an rf Paul trap.\footnote{C.~J.~Campbell \textit{et al.}, \textit{Phys. Rev. Lett} \textbf{102}, 233004 (2009).} Unlike many ions commonly utilized in precision measurements, the trap lifetime of Th$^{3+}$ is limited to only several minutes. This is a severe limitation to experiments involving $^{229}$Th as it is only available in minute quantities. Here we have studied the loss mechanisms by introduction of various contaminants and analyzed reaction products using trapped ion mass spectrometry techniques.\footnote{L.~R.~Churchill \textit{et al.}, \textit{Phys. Rev. A} \textbf{83}, 012710 (2011).}