A new research by University of Liverpool scientists, in collaboration with an international team, has shed light on what happens at the extremes of neutron and proton numbers in search of where the periodic table of chemical elements ends.
In a study published in the journal Nature, the researchers unveil crucial findings regarding the composition of the atomic nuclei of fermium (element 100) and nobelium (element 102), focusing on isotopes with varying neutron counts.
Elements located at the far end of the periodic table do not exist in nature, and they must be synthesized through advanced accelerator-driven nuclear reactions or reactor-breeding techniques for analysis. By employing cutting-edge laser spectroscopy, the team was able to determine the nuclear radius for several isotopes of nobelium and fermium.
In contrast to lighter areas of the nuclear chart, where noticeable changes occur when crossing shell closures, the trend across a significant neutron number appears to be consistent. This suggests that the effects of nuclear shells from a small number of nucleons diminish as one approaches the so-called superheavy elements, causing the nuclei to resemble a deformed liquid drop more closely.
Researchers from the University of Liverpool’s Department of Physics, including Professor Bradley Cheal and Dr Charlie Devlin, played a role in the experimental activities involving nobelium for this study. Their work included operating laser equipment to investigate nobelium atoms and assess their atomic hyperfine structure.
A crucial isotope was generated from the decay of lawrencium atoms, which were sourced from a beam of nuclear reaction products, pulse-heated off a catcher filament, resonantly ionized, and subsequently identified by their distinct alpha decay profile. Their perspective on the broader context led to the proposal of merging the two studies into a single high-impact publication to explore a shared theme.
“A perennial question in nuclear physics is to ask what happens at the extremes of neutron and proton numbers and where the periodic table may end,” said Professor Bradley Cheal, who is also the co-spokesperson for the Nobelium experiments. “This study provides new answers to this. Here at Liverpool, we played an important role in the nobelium experiments that form part of this study. This work combined our expertise in laser spectroscopy, a method traditionally limited to radioactive isotopes of naturally occurring elements, with a track record at specialist facilities capable of producing the heaviest elements.”
Journal reference:
- Jessica Warbinek et al. Smooth trends in fermium charge radii and the impact of shell effects. Nature, 2024; DOI: 10.1038/s41586-024-08062-z
