The thorium-229 based nuclear clock: VUV and Laser Spectroscopy

Updated: 3 months ago
Deadline: 30 Jun 2022

(ref. BAP-2022-385)

Laatst aangepast : 31/05/2022

The Institute of Nuclear and Radiation Physics (IKS) is active in the fields of nuclear physics for fundamental and societal research. It has about 50 researchers and 5 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 from the halo nuclei in the lightest elements to the actinides and super-heavy elements, from neutron-deficient to neutron-rich, employing various experimental techniques at CERN, GSI, and GANIL . These includes laser ionization spectroscopy techniques, radiation detector systems and VUV spectrometry. The Nuclear Spectroscopy Group operates an in-house laser lab with high repetition rate pulsed dye laser systems and a mass separator lab for research on stable and long-lived radioactive isotopes.


This post-doc position is opened in the framework of the thorium-229 (229m-Th)isomer study. This unique nuclear isomer at an excitation energy of around 8 eV (corresponding to a VUV transition of about150 nm) should allow to built a nuclear clock that outperforms the precision of current atomic clock by at least an order of magnitude. While this unique isomer has been proposed four decades ago, it is only recently that its existence has been firmly established experimentally. In 2021, our group managed to observe the radiative decay (which is an essential ingredient to develop a nuclear clock) and to determine the excitation energy with an improved precision (necessary for searches with laser excitation).

Our group initiated a project to produce and study the 229m-Th isomer following two complementary routes. A new approach to produce pure samples of the 229m-Th isomer via laser ionization is under development in the local laser and mass separator labs, and the production of an intense source of 229m-Th populated via the beta decay of 229-Ac (produced at ISOLDE-CERN (Switzerland)) and used to perform VUV spectroscopy  has been commissioned. Both projects address complementary aspects and hold promising opportunities. 

- At KU Leuven, pure beams of singly and doubly charged thorium-229 isotopes have been produced and are now ready to perform laser ionization spectroscopy to determine the moments and charge radii. 

- After the initial VUV spectroscopy experiment performed at ISOLDE (CERN), the tailored VUV spectrometer will be upgraded and used for further detailed studies of the isomer as well of different host material in preparation of a solid-state nuclear clock. 

Both routes will be further exploited at KU Leuven and at ISOLDE and we are looking for a post-doc to support these efforts.


We are looking for enthusiastic and motivated post-doc candidates that have a background in radioactive beam physics, laser and/or VUV spectrometry. You will be fully integrated in the Nuclear Spectroscopy research group and take part in all aspect of the research. Regular travels between the different partner laboratories (TU Vienna and CERN) will take place. 


As a successful candidate, you will be offered the following for the position:

  • 2-year (1 + 1 year) post-doc position within the IKS Nuclear Spectroscopy Group under the supervision of Prof P. Van Duppen
  • Attractive grant
  • A stimulating working environment at a world-leading institution
  • Access to state-of-the-art facilities on site
  • Collaboration with national and international facilities (ISOLDE/CERN, GSI, GANIL)


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

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