Search Efforts for the ²²⁹Th Isomeric Transition

The nucleus of ²²⁹Th has an exceptionally low-energy isomeric transition in the

vacuum-ultraviolet (VUV) spectrum around 8 eV [1] that, if measured with spectroscopic

precision, holds much promise for future timekeeping and quantum logic operations.

Our ongoing direct VUV laser search for the transition using thorium-doped crystals [2]

has been supplemented by a conversion-electron Mössbauer spectroscopy scheme using a

target with electroplated ²²⁹Th [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 our parallel effort to measure the energy of the isomeric decay using a superconducting

nano-wire single photon imager.

[1] Seiferle, B. et al. Energy of the 229Th nuclear clock transition. Nature (2019).

[2] Tkalya, E. V. et al.: Phys. Rev. C 92, 054324 (2015)

[3] Seiferle, B. et al. Phys. Rev. Lett. 118, 042501 (2017)