Speaker
Description
The conventional $r$-process predicts the direct population of $^{263}$Fm through successive neutron captures on $^{56}$Fe seed nuclei, with a synthesis timescale of 75–200 ms while accounting for fission shielding along the actinide path. The abundance of $^{263}$Fm, normalized to the initial seed nuclei, is expected to lie in the range of 10$^{-5} – 10^{-7}$ [1]. Owing to the deformed shell gap associated with $^{264}$Fm, as predicted by Skyrme Hartree–Fock–Bogoliubov (Skyrme-HFB) models[2], neutron-induced fission of $^{263}$Fm can significantly influence the abundances of nuclei near shell closures. In this work, neutron-induced fission of $^{263}$Fm in a Maxwellian neutron spectrum is investigated within a five-dimensional Langevin framework employing Fourier-over-spheroid shape parameterization and microscopic potential-energy surfaces. The calculated fragment distributions exhibit a single, narrow charge peak centered at Z=50 with a width of two charge units, accompanied by a symmetric mass distribution centered at A=124 with a width of 4.3 mass units. These results indicate that neutron-induced fission of $^{263}$Fm along the $r$-process path provides an efficient production mechanism for neutron-rich Sn isotopes. The authors gratefully acknowledge the financial support provided by the Romanian Ministry of Research, Innovation and Digitalization under Contract PN 23 21 01 06 and by the ELI-RO Program under Contract No. ELI-RO/RDI/2024-007 ELITE.
Reference:
[1] Korobkin et al., On the astrophysical robustness of the neutron star merger r-process, Monthly Notices of the Royal Astronomical Society, Volume 426, Issue 3, 1 November 2012, Pages 1940–1949, https://doi.org/10.1111/j.1365-2966.2012.21859.x
[2] Brenner, D. S., Zamfir, N. V., and Casten, R. F., Evidence for a Spherical Subshell at N=164, Physical Review C, 50(1), 490–492 (1994). https://doi.org/10.1103/PhysRevC.50.490