Testing the possible doubly magic nature of Tin-100, researchers study the electromagnetic properties of indium isotopes
Scientists are closing in on a major cornerstone of nuclear physics, Tin-100
image: Visualization of the evolution of the nuclear size and shape from indium and tin isotopes between the major nuclear shells at N=50 and N=82, where N is the number of neutrons in the nucleus.
Credit: Image courtesy of Jonas Karthein, Massachusetts Institute of Technology
The Science
Atomic nuclei consist of strongly interacting protons and neutrons densely packed into a volume a billion times smaller than the overall atom with its cloud of electrons. Nuclei with a “magic number” of protons or neutrons exhibit particularly simple structures, with relatively small size and spherical shape. This is analogous to the chemical stability of noble gases, where electrons fill so-called shells. These magic numbers for nuclei include 8, 20, 28, 50, 82, and 126, and indicate that the shells that hold protons or neutrons in a nucleus are full. Nuclear physicists are especially interested in the study of nuclei around these magic numbers as their properties are expected to be governed by one or a few single particles. One prime example of doubly magic nuclei is Sn-100, an isotope of tin (Sn) with 50 protons and 50 neutrons. With just a single proton hole with respect to tin, the indium isotopes provide an ideal system to test the doubly magic nature of Sn-100. In this work, researchers used precision laser spectroscopy at the CRIS/ISOLDE facility at CERN to measure, for the first time, the electromagnetic properties of neutron-deficient indium isotopes when approaching the neutron number N=50. The evolution of the nuclear size and deformation of these isotopes revealed parabolic trends with minima at the neutron magic numbers N=50 and N=82. The results were compared to state-of-the-art theoretical calculations supporting a doubly magic structure of Sn-100, establishing an important benchmark for the development of nuclear theory.
The Impact
The results revealed strong evidence for the doubly magic nature of Sn-100. The simple structure of this nuclear system makes it ideal for guiding theoretical understanding of atomic nuclei. The findings should lead to further experiments at facilities such as the Facility for Rare Isotope Beams. These new facilities will enable precise studies of the nuclear properties of Sn-100 and neighboring isotopes. Such work will test scientific knowledge of nuclei at the extreme limits of stability.
Summary
Understanding the nuclear properties near Sn-100, which has been suggested to be the heaviest doubly magic nucleus with a proton number Z equal to its neutron number N, has been a long-standing challenge for experimental and theoretical nuclear physics. In this study, an international team used precision laser spectroscopy at the CRIS/ISOLDE facility at CERN to measure the ground-state electromagnetic moments and nuclear charge radii of neutron deficient indium (Z = 49) isotopes approaching N=50. The results reveal parabolic trends as a function of the neutron number, with a reduction towards these two closed neutron shells, N=50 and N=82, supporting a doubly magic character for Sn-100. A detailed comparison between the experiments and theoretical results exposed deficiencies in nuclear models and established a benchmark for future theoretical developments.
Funding
This work was supported by ERC Consolidator (FNPMLS); STFC grants and Ernest Rutherford; by the Department of Energy Office of Science, Office of Nuclear Physics; the BriX Research Program; the FWO-Vlaanderen (Belgium); the European Union’s Grant Agreement; the Polish National Science Centre; a Leverhulme Trust Research Project Grant; the National Key R&D Program of China; the National Natural Science Foundation of China; the Deutsche Forschungsgemeinschaft Project; the European Research Council under the European Union’s Horizon 2020 research and innovation program; the Natural Sciences and Engineering Research Council of Canada; the Arthur B. McDonald Canadian Astroparticle Physics Research Institute. Additional support was provided by a Feodor-Lynen postdoctoral Research Fellowship of the Alexander-von-Humboldt Foundation, computational resources allocated by the CSC-IT Center for Science Ltd.; the University of York’s high-performance Viking Cluster and Research Computing team; computing resources on Cedar at WestGrid; the Digital Research Alliance of Canada; the Jülich Supercomputing Center; use of the ParamVikram-1000 HPC facility at the Physical Research Laboratory in India; and the Indian Department of Space.