Isoscaling studies of fission: A sensitive probe into the dynamics of scission

The fragment yield ratios were investigated in the fission of ${}^{238,233}\mathrm{U}$ targets induced by $14\text{MeV}$ neutrons. The isoscaling behavior was typically observed for the isotopic chains of fragments ranging from the proton-rich to the most neutron-rich ones. The observed high sensitivity of neutron-rich heavy fragments to the target neutron content suggests fission as a source of neutron-rich heavy nuclei for present and future rare ion beam facilities, allowing studies of nuclear properties towards the neutron drip line and investigations of the conditions for nucleosynthesis of heavy nuclei. The breakdowns of the isoscaling behavior around $N=62$ and $N=80$ manifest the effect of two shell closures on the dynamics of scission. The shell closure around $N=64$ can be explained by the deformed shell. The investigation of isoscaling in the spontaneous fission of ${}^{248,244}\mathrm{Cm}$ further supports such conclusion. The $Z$ dependence of the isoscaling parameter exhibits a structure which can be possibly related to details of scission dynamics. The fission isoscaling studies can be a suitable tool for the investigation of possible new pathways to synthesize still heavier nuclei.

Figure 1

Ratios of the fragment yields from the fission of ${}^{238,233}\mathrm{U}$ targets induced by $14\text{MeV}$ neutrons [15]. The data are shown as alternating solid and open circles. The labels apply to the larger symbols. The lines represent exponential fits. For clarity, the $R_{21}$ dependences are shifted from element to element by one unit. Nearly vertical lines mark major isoscaling breakdowns.

Figure 2

Ratios of the fragment yields from the spontaneous fission of ${}^{248,244}\mathrm{Cm}$ [15]. The data are shown as alternating solid and open circles. The labels apply to the larger symbols. The lines represent exponential fits. For clarity, the $R_{21}$ dependences are shifted from element to element by one unit. Vertical lines mark major isoscaling breakdowns.

Figure 3

The systematics of (a) isoscaling parameter $\alpha$ in the fission of ${}^{238,233}\mathrm{U}$ targets induced by $14\text{MeV}$ neutrons (b) estimates of apparent fragment temperatures obtained using Eq. (2) (for details see text), and (c) corresponding fragment excitation energies as a function of the atomic number $Z$.