Speaker
Description
The exotic isotopes in the Ca region ($Z = 20$) have attracted significant experimental and theoretical attention due to the proposed shell closures at neutron numbers $N = 32,34$ [1-5]. In particular, the subshell closure at $N=32$ represents a puzzling case, since the unexpectedly large charge radius of $^{52}$Ca [2] challenges the magicity of this isotope. The lack of a consistent theoretical explanation behind the mechanism driving the evolution of the charge radii in this region of the nuclear chart continues to motivate theoretical and experimental advances.
The hyperfine structure of $^{52}$K ($N = 33$) was measured with the Collinear Resonance Ionization Spectroscopy (CRIS) technique [6]. This work demonstrates for the first time the combination of the CRIS method with beta-detection, paving the way for future measurements on radioactive beams that are heavily contaminated with stable or long lived isotopes. Our result represents the first measurement of a charge radius beyond $N = 32$ in the Ca region, allowing us to investigate if the stabilizing effect of a shell closure is present at this proposed magic number.
The experimental results are furthermore compared to state-of-the-art coupled cluster and energy density functional calculations with the aim to explore the mechanisms behind the large charge radii of isotopes in this region.
REFERENCES
[1] Garcia Ruiz, R.F. et al., Nature Physics 12, 594-598 (2016).
[2] Wienholtz, F. et al., Nature 498, 346 (2013).
[3] Steppenbeck, D. et al., Nature 502, 207 (2013).
[4] J. Bonnard, S. M. Lenzi, and A. P. Zuker PRL. 116, 212501 (2016)
[5] Miller, A.J, et al., Nature Physics 15, 432-436 (2019).
[6] Flanagan, K.T., et al., PRL 111.21 (2013): 212501.