Alternative approach to populate and study the Th-229 nuclear clock isomer

M. Verlinde, S. Kraemer, J. Moens, K. Chrysalidis, J.G. Correia, S. Cottenier, H. De Witte, D.V. Fedorov, V.N. Fedosseev, R. Ferrer, L.M. Fraile, S. Geldhof, C.A. Granados, M. Laatiaoui, T.A.L. Lima, P.-C. Lin, V. Manea, B.A. Marsh, I. Moore, L.M.C. Pereira, S. Raeder, P. Van den Bergh, P. Van Druppen, A. Vantomme, E. Verstraelen, U. Wahl, S.G. Wilkins
Physical Review C
100, 2


A new approach to observe the radiative decay of the Th-229 nuclear isomer, and to determine its energy and radiative lifetime, is presented. Situated at a uniquely low excitation energy, this nuclear state might be a key ingredient for the development of a nuclear clock or a nuclear laser and, the search for time variations of fundamental constants like the fine structure constant. The isomer's gamma decay towards the ground state will be studied with a high-resolution vacuum ultraviolet (VUV) spectrometer after its production by the beta decay of Ac-229. The novel production method presents a number of advantages asserting its competitive nature with respect to the commonly used U-233 alpha-decay recoil source. In this paper, a feasibility analysis of this new concept, and an experimental investigation of its key ingredients, using a pure Ac-229 ion beam produced at the ISOLDE radioactive beam facility, is reported.