Effect of Shell Structure on Fission Isoscaling

Abstract

Recently, the fragment yield ratios were investigated in the fission of 238,233U targets induced by 14 MeV neutrons [1]. The effect of the deformed shell structure around N=64 on the dynamics of scission was suggested as an explanation of the observed breakdown of the isoscaling behavior. As an alternative explanation, the effect of binding energy of final fragments, in particular the neutron shell closure of the complementary fragment around N=82, was suggested by Friedman [2]. When applying that concept consistently, the observed two breakdowns of the isoscaling behavior around N=62 and N=80 signal the effect of two shell closures (N=82 and N=64) on the dynamics of scission. To separate the two effects, we examine the isoscaling plots obtained using fission fragment yield data from the spontaneous fission of the heavier nuclei 248,244Cm and find that the breakdown of isoscaling around N=64 persists even if it can not be related to shell closure of the complementary fragment and thus it manifests the effect of the deformed shell structure in the scission configuration.