Jun 13 – 17, 2022
Berkeley, CA
US/Pacific timezone

Vacuum Ultraviolet Spectroscopy of the low lying Thorium-229 isomer

Not scheduled
Berkeley, CA

Berkeley, CA

Lawrence Berkeley National Laboratory
Oral Oral Presentations NS2022 Plenary


Dr Premaditya Chhetri (KU Leuven)


Owing to its very low excitation energy the isomer of thorium-229 has been proposed as a candidate for a possible future frequency standard, a nuclear clock and is expected to outperform the current atomic clocks [1,2]. Currently, the best values of the excitation energy are 8.28(17) eV and 8.10(17) eV [3,4]. These were measured using two different techniques where the population of the isomer was achieved via the α-decay of uranium-229. However, a precise knowledge of the isomer excitation energy is a necessary for the development of an optical clock.

Recently, spectroscopy measurement has been possible using an alternative approach of populating the isomer via the beta decay of actinium-229 [5]. The laser ionized actinium-229 ions produced online at CERN’s ISOLDE facility were implanted onto a large bandgap crystal at specific lattice positions. A favourable feeding fraction of the isomer from the beta decay of actinium-229 compared to that via the alpha decay of uranium-229 and a low beta energy compared to alpha decay leads to a significantly reduced radioluminescence. This allowed us to study the VUV-photons stemming from the radiative decay of the isomer for the first time resulting in a much precise determination of the energy and lifetime of the isomer.
In this contribution, a dedicated setup developed at KU Leuven for the implantation of an actinium-229 beam into large-bandgap crystals and the vacuum-ultraviolet spectroscopic study of the emitted photons will be presented.

[1] E. Peik et al., Europhys. Lett. 61, 2 (2003)
[2] C. Campbell et al., Phys. Rev. Lett. 108, 120802 (2012)
[3] B. Seiferle et al., Nature 573, 243-246 (2019)
[4] T. Sikorsky et al., Phys. Rev. Lett. 125, 142503 (2020)
[5] M. Verlinde et al., Phys. Rev. C 100, 024315 (2019)

Primary authors

Dr Premaditya Chhetri (KU Leuven) Ms Silvia Bara (KU Leuven) Mr Kjeld Beeks (Vienna University of Technology) Prof. Michael Block (GSI, HIM Mainz, University of Mainz) Prof. Thomas Cocolios (KU Leuven) Dr J.G. Correia (CERN) Dr Hilde De Witte (KU Leuven) Dr Rafael Ferrer (KU Leuven) Dr Sarina Geldhof (KU Leuven) Mr Fedor Ivandikov (KU Leuven) Dr Yuri Koudriavtsev (KU Leuven) Prof. Ulli Köster (Institut Laue-Langevin) Mr Sandro Kraemer (KU Leuven) Dr Mustapha Laatiaoui (HIM Mainz, University of Mainz) Dr Razvan Lica (CERN) Dr Vladimir Manea (IPN Orsay) Mr Janni Moens (KU Leuven) Prof. Iain Moore (University of Jyväskylä) Prof. Lino Pereira (KU Leuven) Dr Sebastian Raeder (GIS, HIM Mainz) Dr Sebastian Rothe (CERN) Dr Antoine de Rpubin (KU Leuven) Prof. Thorsten Schumm (Vienna University of Technology) Dr Benedict Seiferle (LMU Munich) Dr Simon Sels (KU Leuven) Prof. Peter Thirolf (LMU Munich) Mr Paul Van Den Bergh (KU Leuven) Prof. Piet Van Duppen (KU Leuven) Prof. André Vantomme (KU Leuven) Prof. Ulrich Wahl (Universidade de Lisboa) Mr Arno Claessens (KU Leuven)

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