An improved unified fission model for α-decay half-lives

Abstract

An improved unified fission model (IMUFM) is developed for α-decay half-lives by introducing an analytical expression of the equivalent assault frequency and using a modified version of Woods-Sanox potential. The parameters of the analytical expression are determined by fitting the experimental α-decay half-lives from the ground state to ground state transitions. By comparing the agreement between the calculated ones and the experimental half-lives, it is found that the accuracy of IMUFM is improved significantly than its predecessor. Then the IMUFM is extended to study the α-decay properties of the superheavy nuclei with Z=118-120 isotopes. The α-decay half-lives of these nuclei are predicted within the IMUFM by inputting the $Q_{\alpha }$ values that extracted from the Weizsäcker-Skyrme-4 (WS4) model, the finite-range droplet model (FRDM) and the Koura-Tachibaba-Uno-Yamada (KTUY) formula, respectively. By observing the evolution of the $Q_{\alpha }$ values and the half-lives of Z=118-120 isotopes versus the neutron number N, the shell effects at N=178 and N=184 are shown evidently. At last, the dominant decay modes of ${}^{296}118$, ${}^{297}119$ and ${}^{298}120$ α-decay chains are investigated by studying the competition between α-decay and spontaneous fission (SF), which might be helpful for identifying these nuclides in future experiments.