Speaker
Description
Due to its low excitation energy around 8.3 eV, the unique $^{229}$Th isomer is, for now, the only candidate for developing a nuclear clock for, amongst others, fundamental physics studies~\cite{peik2015nuclear,thirolf2019improving}. In the past, measuring the isomer's radiative decay from a large-bandgap crystal with $^{229\text{m}}$Th embedded, has proven difficult: the commonly used population of the isomer via the $^{233}$U $\alpha$-decay has a limited branching ratio towards the isomer and creates a high-radioluminescence background \cite{verlinde2019,beeks2022nuclear}. However, recently, a new approach to populate the isomer through the $\beta$-decay of $^{229}$Ac was proposed \cite{verlinde2019}. This approach made it possible to observe, for the first time, the radiative decay of the $^{229}$Th isomer with vacuum-ultraviolet (VUV) spectroscopy, which allowed to successfully determine the resulting photon's wavelength at a value of $\lambda = 148.7\pm 0.4$ nm ($E=8.338\pm 0.024$ eV)\cite{kraemer2023observation,thesis_sandro}. Building on this work, a new measurement campaign in July 2023 took place at ISOLDE, aimed at, amongst others, reducing the systematic uncertainty on the energy and accurately determining the half-life of $^{229\text{m}}$Th, embedded in different crystals. Dedicated on-line measurement sequences of the VUV spectrometer were performed to reduce the systematic uncertainty reported in~\cite{kraemer2023observation,thesis_sandro}. We will report the results of these studies, as well as the plans to upgrade the VUV spectrometer that are implemented to further investigate the isomer's time behaviour in different crystals, and under different conditions.
@article{verlinde2019,
author = {M. Verlinde et al.},
title = {Alternative approach to populate and study the $^{229}${T}h nuclear clock isomer},
year = {2019},
journal = {Phys. Rev. C100},
pages = {024315}
}
@article{Kraemer2022_obsRad,
author = {S. Kraemer et al.},
title = {Observation of the radiative decay of the $^{229}${T}h nuclear clock isomer},
year = {2022},
journal={arXiv},
pages={2209.10276}
}
@phdthesis{thesis_sandro,
author = {S. Kraemer},
title = {Vacuum-ultraviolet spectroscopy of the radiative decay of the low-energy isomer in $^{229}${T}h},
school = {KU Leuven - Instituut voor Kern- en Stralingsfysica},
year = {2022}
}
@article{kraemer2023observation,
title={Observation of the radiative decay of the $^{229}${T}h nuclear clock isomer},
author={S. Kraemer et al.},
journal={Nature},
volume={617},
number={7962},
pages={706--710},
year={2023},
publisher={Nature Publishing Group UK London}
}
@article{thirolf2019improving,
title={Improving our knowledge on the $^{229m}$Thorium isomer: Toward a test bench for time variations of fundamental constants},
author={Thirolf, P. and others},
journal={Annalen der Physik},
volume={531},
number={5},
pages={1800381},
year={2019},
publisher={Wiley Online Library}
}
@article{peik2015nuclear,
title={Nuclear clocks based on resonant excitation of $\gamma$-transitions},
author={Peik, E. and Okhapkin, M.},
journal={Comptes Rendus Physique},
volume={16},
number={5},
pages={516--523},
year={2015},
publisher={Elsevier}
}
@article{beeks2022nuclear,
title={The Nuclear Excitation of {T}horium-229 in the {C}a{F}$_2$ Environment},
author={Beeks, KAAG and Schumm, Thorsten},
journal={eng. PhD thesis. Wien: TU Wien},
year={2022}
}
