Isospin dependence of mass-distribution shape of fission fragments of Hg isotopes

Using an improved scission-point model, the mass distributions are calculated for induced fission of even Hg isotopes with mass numbers $A=174\text{to}196$. With increasing $A$ of a fissioning ${}^A$Hg nucleus the mass distribution evolves from symmetric for ${}^{174}$Hg, to asymmetric for isotopes close to ${}^{180}$Hg, and back to more symmetric for ${}^{192,194,196}$Hg. In the fissioning Hg isotopes their excitation energy weakly influences the shape of the mass distribution. In ${}^{180,184}$Hg, the mass distributions of fission fragments remain asymmetric even at high excitation energies.

Figure 1

Calculated (solid line) and experimental [2] (points connected by dashed line) mass distributions of fission fragments for $\beta$-delayed fission of ${}^{180}$Tl (fissioning nucleus is ${}^{180}$Hg).

Figure 2

Calculated mass distributions for the fission of (a) ${}^{174}$Hg, (b) ${}^{176}$Hg, (c) ${}^{178}$Hg, (d) ${}^{180}$Hg, (e) ${}^{182}$Hg, and (f) ${}^{184}$Hg at $l=0$ and excitation energies of 2 (solid lines) and 20 MeV (dashed lines) above the corresponding fission barriers.

Figure 3

The same as in Fig. 2, but for the fission of (a) ${}^{186}$Hg, (b) ${}^{188}$Hg, (c) ${}^{190}$Hg, (d) ${}^{192}$Hg, (e) ${}^{194}$Hg, and (f) ${}^{196}$Hg.

Figure 4

Calculated mass distributions for the fission of ${}^{180}$Hg with the excitation energies of compound nucleus $E_{CN}^{*}(l=0)=36$ (solid line), 44 (dashed-dotted-dotted line), 60 (dashed line), 84 (dotted line), and 108 MeV (dashed-dotted line).

Figure 5

Calculated mass distributions for the fission of ${}^{184}$Hg with the excitation energies of compound nucleus $E_{CN}^{*}(l=0)=34.5$ (solid line), 42.2 (dashed-dotted-dotted line), 58 (dashed line), 81.5 (dotted line), and 105 MeV (dashed-dotted line).