  The fragment yield ratios were investigated in the fission of 238,233U
targets induced by 14 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 248,244Cm 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.
