Search Efforts for the Thorium-229 Nuclear Isomeric Transition

The nucleus of $^{229}$Th has an exceptionally low-energy isomeric transition in the vacuum-ultraviolet (VUV) spectrum around 8 eV [1,2]. While inaccessible to standard nuclear physics techniques, there are various prospects for a laser-accessible nuclear transition. Our ongoing direct VUV laser search for the transition using thorium-doped crystals will be supplemented by a conversion-electron M\"{o}ssbauer spectroscopy scheme [3]. In both of these direct excitation schemes, a pulsed dye laser system is used to generate the tunable VUV light. We will also report on the progress of an indirect measurement of the isomeric decay using a superconducting nano-wire single photon imager. \newline \newline [1] Seiferle, B. et al. Energy of the 229Th nuclear clock transition. Nature (2019). \newline[2] B. R. Beck et al.: LLNL-PROC-415170 (2009) \newline[3] von der Wense, L.C. et al. Hyperfine Interact (2019)