Precise measurements of the evolution of the mean-square charge radius along isotopic chains offer unique insight into nuclear shell structure, collective phenomena, and the underlying forces. Collective nuclear properties are commonly enhanced in open-shell nuclei and significantly reduced around closed nuclear shells. The tin isotopic chain, with its closed proton shell at Z = 50, is of particular importance. Currently, it offers a long sequence of isotopes available for study, stretching across the major neutron shell closures at N = 50 and N = 82. This unique landscape makes the tin chain a fertile testing ground for the development of theoretical ab initio models. While the doubly magic nature of 132Sn (Z = 50 and N = 82) has been well-established experimentally, significantly less data are available to understand the evolution of nuclear structure properties in the region from midshell down towards doubly magic 100Sn (Z = 50 and N = 50).
In a recent article published in Physical Review Letters, the COLLAPS and CRIS collaborations at ISOLDE-CERN, Geneva, present nuclear charge radii measurements for the tin isotopes 104–134Sn, using two collinear laser spectroscopy techniques. The neutron-deficient isotopes, down to 104Sn, were investigated with the collinear resonance ionization spectroscopy (CRIS) setup, while the neutron-rich isotopes, up to 134Sn, were measured using the collinear laser spectroscopy (COLLAPS) experiment. The measurement campaigns thus extend the available data by four isotopes on the neutron-deficient side 104–107Sn and the tin isotope 133Sn in the neutron-rich region. These measurements clarify the archlike trend in charge radii along the tin isotopic chain and reveal an odd-even staggering - i.e. increase or decrease in charge radii when switching between odd and even neutron numbers - that is more pronounced near the N = 50 and N = 82 shell closures.
The measured charge radii of 104–134Sn are interpreted utilizing ab initio valence space in-medium similarity renormalization group (VS-IMSRG) calculations as well as nuclear density functional theory (DFT). The observed local trends are well described by both VS-IMSRG and DFT. Both approaches are able to describe the general behavior of the charge radii. The general features are better predicted near the shell closures. Both theories predict appreciable contributions from beyond-mean-field correlations to the charge radii of the neutron-deficient tin isotopes. The models, however, fall short of reproducing the observed odd-even staggering in the midshell and the magnitude of the known electric quadrupole transition probabilities B(E2). This highlights the remaining challenges in achieving a unified description of both ground-state properties and collective phenomena.
Please read more in the Physical Review Letters article.
Original publication:
Charge Radii Measurements of Exotic Tin Isotopes in the Proximity of N = 50 and N = 82
F. P. Gustafsson, L. V. Rodríguez, R. F. Garcia Ruiz, T. Miyagi, S. W. Bai, D. L. Balabanski, C. L. Binnersley, M. L. Bissell, K. Blaum, B. Cheal, T. E. Cocolios, G. J. Farooq-Smith, K. T. Flanagan, S. Franchoo, A. Galindo-Uribarri, G. Georgiev, W. Gins, C. Gorges, R. P. de Groote, H. Heylen, J. D. Holt, A. Kanellakopoulos, J. Karthein, S. Kaufmann, Á. Koszorús, K. König, V. Lagaki, S. Lechner, B. Maass, S. Malbrunot-Ettenauer, W. Nazarewicz, R. Neugart, G. Neyens, W. Nörtershäuser, T. Otsuka, P.-G. Reinhard, N. Rondelez, E. Romero-Romero, C. M. Ricketts, S. Sailer, R. Sánchez, S. Schmidt, A. Schwenk, S. R. Stroberg, N. Shimizu, Y. Tsunoda, A. R. Vernon, L. Wehner, S. G. Wilkins, C. Wraith, L. Xie, Z. Y. Xu, X. F. Yang, and D. T. Yordanov
Phys. Rev. Lett. 135, 222501 (2025)
DOI: https://doi.org/10.1103/wbdx-k3cd
Weblinks:
COLLAPS Website (ISOLDE-CERN)
CRIS Website (ISOLDE-CERN)
COLLAPS page of division Blaum at MPIK
Group of A. Schwenk at TU Darmstadt
