VUV spectroscopy of the Th-229 isomer: a step towards a nuclear clock

Katholieke Universiteit Leuven
September 24, 2023
Offerd Salary:Negotiation
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VUV spectroscopy of the Th-229 isomer: a step towards a nuclear clock

(ref. BAP-2023-584)

Last modification : Thursday, August 24, 2023

The Institute of Nuclear and Radiation Physics (IKS) of the Department of Physics and Astronomy is active in the field of nuclear physics for fundamental and societal research. It has about 50 researchers and 7 professors, and graduates 3-5 PhD students per year. The IKS expertise is situated in radioactive and stable ion beam research and applications, and nuclear physics research with laser, decay, orientation and reaction techniques. Within the IKS, the Nuclear Spectroscopy Group of Prof P. Van Duppen studies the fundamental nature of the atomic nucleus focusing on actinides and super-heavy elements, from neutron-deficient to neutron-rich hereby employing various experimental techniques at the KU Leuven laser and detector laboratories and at CERN, GSI, and GANIL.

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This post-doc position is opened in the framework of the Th-229 nuclear clock isomer study. This unique nuclear isomer at an excitation energy of around 8.3 eV (corresponding to a VUV transition of about 150 nm) should allow to built a nuclear clock of interest for fundamental as well as applied research. While this unique isomer has been proposed four decades ago, it is only since 2016 that its existence has been firmly established experimentally.

At KU Leuven, a project was initiated to produce and study the Th-229 isomer following two complementary routes. A new approach to produce pure samples of the Th-229 isomer via laser ionization is under development in the local laser and mass separator labs, and the production of an intense source of Th-229 isomer populated via the beta decay of Ac-229 (produced at ISOLDE-CERN (Switzerland)) has been initiated. Both projects address complementary aspects. The approach using Ac-229 radioactive ion beams implanted in CaF2 and MgF2 crystals, resulted in the first observation of the radiative decay and a first measurement of the life time of the isomer. The results were recently published in "Observation of the radiative decay of the 229Th nuclear clock isomer" S. Kraemer et al., Nature 617 (2023) 706. In future campaigns, the radiative decay and half-life measurements will be performed in different large-band gap crystals and under different implantation conditions. For this purpose the VUV spectrometer needs to be upgraded and fully characterized.

You will be fully integrated in the Th-229 research group and take part in all aspect of the research.

Regular travels between the different partner laboratories (Vienna and CERN) will take place and skills in the field of experimental nuclear or VUV spectroscopy are a plus.


You have a critical mind and you hold a PhD degree in atomic, nuclear physics or equivalent. We are looking for enthusiastic and selfmotivated post-doc researchers.

Experience with radiation detection systems is necessary.

Expertise in radioactive ion beam science is a plus.


We offer a 12-month post-doc position (renewable up to 3 years, provided this doesn't pass a 6 years period after obtaining a PhD). The position will remain open until filled or until the deadline.


For more information please contact Prof. dr. Piet Van Duppen, tel.: +32 16 32 72 72, mail: [email protected].

KU Leuven seeks to foster an environment where all talents can flourish, regardless of gender, age, cultural background, nationality or impairments. If you have any questions relating to accessibility or support, please contact us at [email protected].

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