Physicists have confirmed the existence of a double magic number in the core of lead-100.
Atoms consist of a nucleus surrounded by an electron shell. Inside the nucleus are positively charged protons and neutral neutrons. An element may have several isotopes, which are variations differing in the number of neutrons in the nucleus. For instance, oxygen has 18 isotopes: all of them have eight protons, but the number of neutrons ranges from two to 20.
In nuclear physics, certain numbers of protons and neutrons in the nucleus — 2, 8, 20, 28, 50, and 82 — are referred to as "magic numbers." This indicates that such atomic nuclei have fully filled nuclear shells and exhibit high stability. They resist deformation well and possess high symmetry.
If both magic numbers of protons and neutrons are present in the nucleus, that isotope is termed "doubly magic." It has an especially strong structure, which researchers are studying to test nuclear physics theories.
Due to its short lifespan and the complexity of its production, tin-100 has been challenging to study for a long time. Physicists could not confidently determine whether it possesses "double magic." Additionally, there was a lack of data regarding the size and shape of nuclei close to 100Sn to confirm its structure.
Recently, CERN (the European Organization for Nuclear Research) gathered enough data to confirm the doubly magic state of tin-100. The results provide confidence that 100Sn has a doubly magic nucleus with 50 protons and 50 neutrons. These findings open new avenues for nuclear physics, allowing for the creation of more accurate theoretical models.
For more detailed investigations, scientists worked with isotopes of indium. They contain one proton less than tin-100. This indium has become an excellent laboratory model for studying the evolution of nuclear structure near the magic stable state of tin-100. The development of highly sensitive laser spectroscopy methods enabled scientists to conduct the necessary measurements.
Theoretical nuclear physics is also progressing. Modern models are increasingly accurately describing the structure of heavy isotopes. A vast amount of experimental data on the electromagnetic properties of 100Sn has not only confirmed certain aspects of existing theories but also established a new standard for further research and modeling.
“The experiment of collinear resonance ionization spectroscopy (CRIS) at CERN-ISOLDE and the production of exotic indium isotopes at this facility allowed us to perform precise laser spectroscopy of the atomic energy levels of indium, providing information about their nuclear electromagnetic properties,” explained Professor Ronald Garcia Ruiz.
The collected data confirmed the doubly magic nature of tin-100, predicted by theoretical models. For a deeper understanding of the structure of this isotope, the study's lead author, Dr. Jonas Karthein, and colleagues conducted calculations and refined the isotope's structure.
“Our results provide compelling evidence for the doubly magic nature of 100Sn, offering key experimental information for understanding the 'island of stability' of isotopes and resolving discrepancies arising from spectroscopic experiments in different laboratories worldwide. The simple structure of these nuclear systems offers an ideal model for enhancing our theoretical understanding of atomic nuclei,” commented Dr. Karthein.
These findings will assist scientists in developing more accurate models and testing existing theories. Further research is expected to allow even more precise measurements of unstable isotopes, which will help deepen the understanding of the structure and properties of unstable isotopes.
The research is published in the journal Nature Physics.