Zakopane 2026 Conference on Nuclear Physics

Investigating exotic nuclei far from the valley of stability provides crucial insights into nuclear structure and the underlying forces that shape it. The experimental determination of atomic and nuclear properties such as atomic energy levels, ionization potentials, electromagnetic moments, trends in mean-square charge radii, and isotope shifts for nuclei in the region of heavy actinides by laser spectroscopy is difficult. The main challenges are low production rates at accelerator facilities and unfavorable half-lives of the fusion products. This necessitates the use of highly efficient and selective laser spectroscopy techniques. At GSI-FAIR in Darmstadt, Germany, the RAdiation Detected Resonance Ionization Spectroscopy (RADRIS) has been successfully used to study aforementioned properties in $^{245,246,248-250,254}$Fm and $^{252-255}$No [1-3].
The employed detection of laser-ionized atoms via their $\alpha$-decay becomes impractical for nuclei with half-lives on the order of several tens of hours using a single detector. Thus, a more versatile design with eight detectors was developed to increase the method's reach towards longer-lived nuclei. The upgraded detector setup was used in a recent measurement campaign to investigate isotope shifts the element californium. The isotopic chain of $^{240,241,242,244,246}$Cf was studied using laser spectroscopy, revealing trends in the changes of mean-square charge radii. This complements previous investigations of $^{249-253}$Cf at the RISIKO mass separator of the Johannes Gutenberg-University Mainz, Germany [4].

[1] M. Laatiaoui et al., Nature 538, 495–498 (2016)
[2] J. Warbinek et al., Nature 634, 1075–1079 (2024)
[3] S. Raeder, et al., Physical Review Letters, 120(23) 232503 (2018)
[4] F. Weber et al., Atoms, 10(2), 51 (2022)