Speaker
Description
Laser spectroscopy experiments are an indispensable tool in modern nuclear structure studies. Hyperfine structure and isotope shift data such as nuclear moments and charge radii obtained in such experiments serve as tests of state-of-the-art theories[1]. Such data are particularly sparse for heavy and superheavy nuclei[2]. Our collaboration's experiment JetRIS has been successfully applied to the heaviest element with a known resonance ionization scheme, probing the hyperfine structure of the $K=8^-$ isomeric state in No-254.
JetRIS is an in-gas-jet Resonant Ionisation Spectrometry setup[3,4] located at the focal plane of the Separator for Heavy Ion reaction Products (SHIP). A Ca-48 beam on a Pb-208 target was used to produce $\sim4\ \mathrm{ions/s}$ of No-254 in a fusion-evaporation reaction. The recoiling ions enter JetRIS through a thin titanium foil, stop in argon gas and remain mostly singly charged. An electrode array is used to transport the ions from the stopping volume to a negatively biased and heated tantalum filament. Nobelium atoms are desorbed from the filament and carried by gas flow through a de Laval nozzle and into the collimated hypersonic gas jet, where two-step resonant laser ionisation takes place. The created photo-ions are guided to an alpha detector, which is used to ensure background-free measurements at low production rates.
In this talk, we report on the measured hyperfine spectra, the deduced nuclear moments as well as the isomer shift of the short-lived $K=8^-$ isomer in No-254 ($T_{1/2}=259\ \mathrm{ms}$), addressing the currently disputed[5-8] quasiparticle configuration of the state. Additionally, we present the technical development of the setup that resulted in fast extraction ($<\!100\ \mathrm{ms}$) and improved efficiency enabling these measurements. Finally, we highlight the potential applications of the in-gas-jet technique for isotope/isomer separation and the ongoing work applying it to radioactive molecules.
References
[1] M. Block et al., Prog. Part. Nucl. Phys. 116, 103834 (2021).
[2] X. F. Yang et al., Prog. Part. Nucl. Phys. 129, 104005 (2023).
[3] J. Lantis et al., Phys. Rev. Res. 6, 023318 (2024).
[4] S. Raeder et al., Nucl. Instrum. Methods Phys. Res. B 463, 272–276 (2020).
[5] S. K. Tandel et al., Phys. Rev. Lett. 97, 082502 (2006).
[6] R.-D. Herzberg et al., Nature 442(7105), 896–899 (2006).
[7] R. M. Clark et al., Phys. Lett. B 690(1), 19–24 (2010).
[8] S. G. Wahid et al., Phys. Rev. C 111, 034320 (2025).
| Email address | fedor.ivandikov@kuleuven.be |
|---|---|
| Supervisor's Name | Piet Van Duppen |
| Supervisor's email | piet.vanduppen@kuleuven.be |
| Classification | Applications of radioactive ion beams |
