Orateur
Description
Laser spectroscopic techniques have become essential tools for probing the properties of nuclei produced at radioactive ion beam (RIB) facilities. By exploiting the interaction between nuclear and electronic structures, key nuclear observables such as electromagnetic moments, nuclear spins, and mean-squared charge radii can be extracted from measurements of hyperfine structures and isotope shifts [1]. These quantities provide critical benchmarks for advancing modern nuclear theory and improving our understanding of nuclear structure.
Nonetheless, a persistent limitation remains in the trade-off between achievable resolution and sensitivity. This is evident in the lack of measurements of nuclear electromagnetic moments beyond the electric quadrupole moment in radioactive nuclei. Probing the next order, namely the magnetic octupole moment, would provide a new observable to investigate core polarization and effective-current contributions [2]. Moreover, measurements along chains of radioactive isotopes will enable the systematic exploration of how octupole moments evolve with changes in nuclear composition. Such studies will help isolate and quantify contributions from core polarization, pairing effects, and shell evolution, thereby improving the predictive power of both shell-model and mean-field approaches [3].
At the IGLIS facility at KU Leuven [4], in collaboration with LPC Caen, we have recently developed a novel spectroscopic technique based on established in-gas-jet resonance ionization spectroscopy [5] and Laser Radiofrequency Double Resonance (LRDR) techniques [6]. This approach combines the high sensitivity of the former with the resolution achievable with the LRDR method. It enables the measurement of hyperfine structure splittings at the kHz level, representing a three-order-of-magnitude improvement over state-of-the-art high-resolution laser spectroscopy methods applied to radioactive atoms, while maintaining efficiencies comparable to the standard in-gas-jet resonance ionization method. Moreover, the homogeneous and collision-free gas-jet environment has been shown to provide long coherence times, enabling the manipulation of the quantum state of the atomic ensemble via Rabi oscillations and Ramsey excitations.
Overall, these developments provide a significant enhancement of experimental capabilities for the study of radioactive nuclei, particularly in connection with the development of new radioactive ion beam facilities such as S$^3$-LEB [7] at GANIL. This work opens a new window for investigating nuclei across the nuclide chart.
References
[1] Yang, X., et al. Progress in Particle and Nuclear Physics 129 (2020): 104005.
[2] Sen’Kov, R. A., and V. F. Dmitriev. Nuclear Physics A 706.3-4 (2002): 351-364.
[3] de Groote, R. P., et al. Physics Letters B 827 (2022): 136930.
[4] Kudryavtsev, Y., et al. Nuclear Instruments Methods B 376 (2016): 345–352.
[5] Ferrer, R., et al. Nature Communication 8.1 (2017): 14520.
[6] Childs, W. J. Physics reports 211.3 (1992): 113-165.
[7] Ajayakumar, A., et al. Nuclear Instruments and Methods B 539 (2023): 102-107.