SAMOP 2023 – wissenschaftliches Programm

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MS: Fachverband Massenspektrometrie

MS 4: Heavy and Superheavy Elements

MS 4.1: Hauptvortrag

Donnerstag, 9. März 2023, 11:00–11:30, F128

Observation of the radiative decay of the thorium-229 nuclear clock isomer — •Sandro Kraemer for the ISOLDE-IS658 collaboration — Instituut voor Kern- en Stralingsfysica, KU Leuven, Belgium — Fakultät f. Physik, LMU München, Germany

A unique feature of thorium-229 is its isomeric first excited state with an exceptionally low excitation energy, proposed as a candidate for future nuclear optical clocks. The development of such an optical clock requires, however, knowledge of the excitation energy by at least an order of magnitude more precise. Additionally, spectroscopic experiments searching for a direct signature of the radiative decay have so far been unsuccessful.

In this work, an alternative approach using the beta decay of actinium-229 is studied as a novel method to populate the isomer with high efficiency and in low background conditions. Produced online at the ISOLDE facility at CERN, actinium is laser-ionized and implanted into a large-bandgap crystal.

A vacuum-ultraviolet spectroscopic study of implanted mass 229 beams at the ISOLDE facility will be presented. From the results obtained during a first measuring campaign it can be concluded that the radiative decay of the thorium-229 isomer has been observed for the first time, the excitation energy of the isomer has been determined with a factor of 5 improved uncertainty and the ionic lifetime in a crystalline environment was constrained.