α-decay chains of recoiled superheavy nuclei: A theoretical study

Abstract

A systematic theoretical study of $\ensuremath{\alpha}$-decay half-lives in the superheavy mass region of the periodic table of elements is carried out by extending the quantum-mechanical fragmentation theory based on the preformed cluster model (PCM) to include temperature $(T)$ dependence in its built-in preformation and penetration probabilities of decay fragments. Earlier, the $\ensuremath{\alpha}$-decay chains of the isotopes of $Z=115$ were investigated by using the standard PCM for spontaneous decays, with``hot-optimum'' orientation effects included, which required a constant scaling factor of ${10}^{4}$ to approach the available experimental data. In the present approach of the PCM $(T\ensuremath{\ne}0)$, the temperature effects are included via the recoil energy of the residual superheavy nucleus (SHN) left after $x$-neutron emission from the superheavy compound nucleus. The important result is that the $\ensuremath{\alpha}$-decay half-lives calculated by the PCM $(T\ensuremath{\ne}0)$ match the experimental data nearly exactly, without using any scaling factor of the type used in the PCM. Note that the PCM $(T\ensuremath{\ne}0)$ is an equivalent of the dynamical cluster-decay model for heavy-ion collisions at angular momentum $\ensuremath{\ell}=0$. The only parameter of model is the neck-length parameter $\ensuremath{\Delta}R$, which for the calculated half-lives of $\ensuremath{\alpha}$-decay chains of various isotopes of $Z=113$ to 118 nuclei formed in ``hot-fusion'' reactions is found to be nearly constant, i.e., $\ensuremath{\Delta}R\ensuremath{\approx}0.95\ifmmode\pm\else\textpm\fi{}0.05$ fm for all the $\ensuremath{\alpha}$-decay chains studied. The use of recoiled residue nucleus as a secondary heavy-ion beam for nuclear reactions has also been suggested in the past.