Fermium studied at GSI/FAIR — Researchers investigate nuclear properties of element 100 with laser light
13-Nov-2024
Artwork of the nuclear chart – The fermium isotopes studied by laser spectroscopy are highligthed.
S. Raeder
An international research team reports on experiments performed at the GSI/FAIR accelerator facility and at Johannes Gutenberg University Mainz to come closer to an answer. They gained insight into the structure of atomic nuclei of fermium (element 100) with different numbers of neutrons. Using forefront laser spectroscopy techniques, they traced the evolution of the nuclear charge radius and found a steady increase as neutrons were added to the nuclei. This indicates that localized nuclear shell effects have a reduced influence on the nuclear charge radius in these heavy nuclei. The results were published in the scientific journal Nature.
Elements beyond uranium (element 92), like for example Fermium (element 100), do not occur naturally in the Earth’s crust. To be studied, they thus have to be produced artificially. They bridge from the heaviest naturally occurring elements to the so-called superheavy elements, which start at element 104. Superheavy elements owe their existence to stabilizing quantum mechanical shell effects, which add about two thousandths of the total nuclear binding energy. Albeit a small contribution, it is decisive in counteracting the repelling forces between the many positively charged protons.
Quantum mechanical effects induced by the building blocks of atomic nuclei, the protons and neutrons, which together make up the nucleus, are explained by the nuclear shell model. Similar to atoms, where filled electron shells lead to chemical stability and inertness, nuclei with filled nuclear shells (containing so-called “magic” numbers of protons/neutrons) exhibit an increased stability. Consequently, their nuclear binding energies and their lifetimes increase. In lighter nuclei, filled nuclear shells are known to also influence trends in the nuclear charge radii.