Probing the delicate balance of the spontaneous fission instability in sub-{\mu}s superheavy nucleus 252Rf

Abstract

Stimulated by the recent experimental discovery of the sub-$\mu$s fission nucleus $^{252}$Rf [Phys. Rev. Lett. 134 (2025) 022501], we perform an improved configuration-constrained potential-energy-surface calculation, revealing the mechanism of intricate balance for the enhanced stability due to the high-$K$ (e.g., $K^\pi = 6^+$) isomer, possibly building on a shape isomeric state. The different deformation and coupling effects, such as triaxial $\gamma$, reflection-asymmetric $\beta_{3}$ and high-order $\beta_{6}$ deformations, are discussed for both ground state and isomeric state based on the corresponding potential-energy curves along the fission valley. In particular, it is pointed out for the first time that possible multipath decay, e.g., from the high-$K$ isomeric state to those states formed between potential energy surfaces of this isomeric state and the ground state during the fission process, may reduce the nuclear lifetime and balance the fission stability. These results elucidate not only the enhanced stability of the high-$K$ isomeric state, including the inversion of stability between it and the ground state, but also the limitation of the stability increase of such an isomeric state.