Stepping into the Sea of Instability: The New Sub-us Superheavy Nucleus 252Rf

TL;DR

This paper reports the discovery of a new superheavy isotope, $^{252}$Rf, with an extremely short half-life, expanding the known range of superheavy nuclei and providing insights into fission stability and high-$K$ isomeric states.

Contribution

The discovery of $^{252}$Rf with a very short half-life and the measurement of its high-$K$ isomeric state, advancing understanding of superheavy nuclei stability.

Findings

$^{252}$Rf has a half-life of about 60 ns.

High-$K$ isomeric state has a half-life of approximately 13 μs.

Ground-state spontaneous fission half-lives decrease towards the neutron-deficient border.

Abstract

We report the discovery of the new isotope $^{252}$Rf. With its extremely short half-life of $60^{+90}_{-30}$~ns, it expands the range of half-lives of the known superheavy nuclei by about two orders of magnitude. This nucleus was synthesized in its high-$K$ isomeric state, for which we measured a half-life of $13^{+4}_{-3}$~$\mu$s. Our results confirm a smooth onset of decreasing ground-state spontaneous fission half-lives in the neutron-deficient Rf isotopes towards the isotopic border of $10^{-14}$~s, which is the time needed to form an atomic shell. Our findings set a new benchmark for further exploration of phenomena associated with high-$K$ states and inverted fission-stability in the heaviest nuclei.