Zero neutron emission in spontaneous fission of252Cf: a form of cluster radioactivity

By using the triple gamma coincidence technique with 20 Ge detectors at the Holifield Laboratory in the spontaneous fission of 252 Cf, neutronless fragmentations, like 104 Mo- 148 Ba, 106 Mo- 146 Ba, 108 Mo- 144 Ba and 104 Zr- 148 Ce, are experimentally observed directly for the first time. When zero neutron emission spontaneous fission occurs, essentially all the available energy goes into the total kinetic energy of the fragments (cold fission). This process is seen theoretically to be an extension of cluster radioactivity, which involves the emission of one light fragment like 14 C, 20 O, (24)Ne or 28 Mg to nearly equal fragments. In the neutronless spontaneous fission reported here, double fine structures (i.e. decays to the excited states of both fragments) are observed experimentally in contrast to fine structure in only the heavy partner populated by the light partner in earlier cluster radioactivity work. Neutronless spontaneous fission is discussed in the framework of cluster radioactivity.