ABSTRACT
Moller et al. have recently performed quantitative calculations of the fission half-lives and potential energy surfaces for mass-symmetric shapes for heavy even-even nuclei from Cm through element 108. Their goal was to search for two fission valleys for symmetric fission, one leading to enlongated shapes with resultant "normal" total kinetic-energy (TKE)s, and the other leading to compact or spherical shapes with very high TKEs. A knowledge of the prompt neutron emission as a function of fragment mass, for each fissioning system is required in order to obtain primary fragment (preneutron emission) mass-yield distributions from radiochemical or kinetic-energy measurements of the fission fragments. Neutron emission has been found to vary significantly with fragment mass, which indicates a large variation in the distribution of excitation energy between the fragments in binary fission. In the process of spontaneous fission, both neutrons and gamma rays may carry away excitation energy from the fragments.
