Microscopic study on asymmetric fission dynamics of Hg180 within covariant density functional theory

Abstract

The asymmetric fission dynamics of $^{180}\mathrm{Hg}$ has been analyzed in the framework of the time-dependent generator coordinate method (TDGCM) based on covariant density functional theory (CDFT) with the relativistic PC-PK1 functional. Three-dimensional $({\ensuremath{\beta}}_{2},{\ensuremath{\beta}}_{3},{q}_{N})$ constrained CDFT calculations have been performed to determine the scission configurations. Remarkably, an asymmetric fission valley is observed in the potential energy surface in the ${\ensuremath{\beta}}_{2}\text{\ensuremath{-}}{\ensuremath{\beta}}_{3}$ plane and the heavy/light fragments at scission are $^{101}\mathrm{Rh}/^{79}\mathrm{Br}$, in good agreement with the data. Furthermore, we find that the heavy fragments of lowest-energy scission configurations, compared to those of other scission points, have rather small quadrupole deformations (${\ensuremath{\beta}}_{2}\ensuremath{\sim}0.4$) and certain octupole deformations (${\ensuremath{\beta}}_{3}\ensuremath{\sim}0.3--0.4$), which are driven by the extended neutron octupole shell gap with $N=56$. Based on the scission configurations, the estimated total kinetic energy distribution is consistent with the trend of experimental data. Finally, the dynamical TDGCM calculation reproduces the asymmetric yield distribution of the low-energy fission of $^{180}\mathrm{Hg}$, especially for the peak positions.