Speaker
Description
For more than half a century, the existence of the island of stability has been theoretically predicted [1]. One of the major topics in nuclear physics is the production of $^{298}$Fl, which is located at the center of this island.
A previous study [2] suggested that the synthesis of a compound nucleus more neutron-rich than $^{298}$Fl (e.g., $^{304}$Fl$^*$) may offer an advantage in terms of production probability. Firstly, due to its lower neutron binding energy, neutrons can be more easily evaporated. Furthermore, neutron emission brings the nucleus closer to the predicted neutron shell closure at $N = 184$, which increases the shell correction energy (which approximates the fission barrier height). These effects help to prevent a significant decrease in survival probability at high excitation energies.
In this study, these mechanisms are theoretically investigated using experimentally studied reaction systems. Particular attention is paid to $^{278}$Ds$^*$ and $^{280}$Ds$^*$ ($Z = 110$), formed via the $^{40}$Ar + $^{238}$U and $^{48}$Ca + $^{232}$Th reactions [3], near the deformed shell region at $N = 162$. These compound nuclei increase their shell correction energies (fission barrier height) via neutron evaporation as they approach $N = 162$.
We calculated the entire fusion-fission process in the superheavy region in three stages: (i) the projectile-target contact, (ii) the competition between fusion and quasi-fission, and (iii) the decay of the excited compound nucleus. We employed the coupled-channel method (CCFULL) [4] for stage (i), the multidimensional Langevin approach [5] for stage (ii), and the statistical model [6] for stage (iii).
In this presentation, we primarily discuss the effect of neutron evaporation and the resulting increase in the shell correction energy (fission barrier height). This effect is likely to offer an advantage in the survival probability of the excited compound nucleus in the decay process. It may also play an important role in reaching the island of stability.
References
[1] W. D. Myers and W. J. Swiatecki, Nucl. Phys. 81, 1 (1966).
[2] Y. Aritomo, Phys. Rev. C 75, 024602 (2007).
[3] Yu. Ts. Oganessian, et al., Phys. Rev. C 109, 054307 (2024).
[4] K. Hagino, et al., Computer Physics Communications 123 (1999) 143–152.
[5] Y. Aritomo, et al., Phys. Rev. C 85, 044614 (2012).
[6] R. Vandenbosch and J. R. Huizenger, Nuclear Fission, pp.227-233 (Academic Press, New York, 1973).