Orateur
Description
Nuclei near doubly magic shell closures are key benchmarks for different theoretical models, as their properties in these regions often exhibit sharp discontinuities. In the lead region ($Z=82$), isotopic chains exhibit a pronounced increase in mean-square charge radii when crossing the neutron shell closure at $N=126$. Although this “kink” feature is systematically observed, its physical origin remains under debate. Different theoretical approaches successfully reproduce the experimental trend but attribute it to distinct mechanisms [1, 2]. Additional experimental data on the mercury ($Z=80$), thallium ($Z=81$) and bismuth ($Z=83$) isotopes in this region, particularly from both ground and isomeric states, is therefore essential to constrain these physical mechanisms.
In this contribution, we present a laser spectroscopy campaign by the RILIS-IDS-ISOLTRAP collaboration targeting mercury, thallium and bismuth isotopes across the $N=126$ shell closure. The powerful in-source laser spectroscopy technique, combined with the decay-tagging method, offers a high-sensitivity approach to deduce changes in mean-square charge radii for both ground and isomeric states. The published data for neutron-rich $^{207-209}$Tl, as well as preliminary results for high-spin isomeric states in $^{212,213}$Bi and ground states in $^{209,210}$Hg, will be presented to probe the influence that the $\nu2g_{9/2}$ and $\nu1i_{11/2}$ single-particle states have on these nuclides. The experimental thallium results are compared with state-of-the-art calculations using TFFS-Fayans functionals to investigate the existence of the kink [3]. In addition, shell effects are observed in the measured nuclear magnetic dipole moments [4]. These trends offer further insight into the evolution of nuclear structure near the N=126 shell closure.
[1] P. M. Goddard et al., Phys. Rev. Lett., vol. 110, p. 032 503, 3 Jan. 2013.
[2] T. Day Goodacre et al., Phys. Rev. Lett., vol. 126, p. 032 502, 3 Jan. 2021.
[3] Z.Yue et al, Phys. Rev. C vol. 110, p. 034 315, 13 Sep. 2024
[4] Z. Yue et al., Physics Letters B 849, 138452 (2024).