Abstract
The 103-min isotope has been identified as the daughter of an electron-capture decay branch of produced via the reaction. Chemical separations were used to confirm the identity of , which decays by spontaneous fission. The kinetic energies of coincident fission fragments were measured, corresponding to a fragment mass which is highly symmetric, similar to those of and . However, the total kinetic energy distribution for is considerably broader (FWHM ∼60 MeV) than those of and , and peaks at 201 MeV, about 35-40 MeV lower in energy. Furthermore, the maximum total kinetic energy of 215 MeV for mass-symmetric events is about 30 MeV lower than for similar events from the spontaneous fission of and . A hypothesis that this energy difference resulted from the emission of light, hydrogen-like particles at scission in a large fraction of spontaneous fission decays was shown to be unfounded. From experiments to observe such particles with counter telescopes, an upper limit of 5% was determined for the fraction of fission events accompanied by light-particle emission. The total kinetic energy deficit at mass symmetry must, therefore, be distributed between internal excitation energy and fragment deformation energy at scission. Although the presence of a large amount of fragment deformation energy seems incompatible with symmetric fission into spherical Sn-like fragments, we prefer this explanation because the low total kinetic energy suggests a lowered Coulomb energy resulting from greater separation of the charge centers of deformed fragments at scission.
RADIOACTIVITY, FISSION (SF); measured , fragment-fragment coin, deduced mass, TKE distributions. ; measured EC decay to , upper limit to SF decay.
- Received 12 April 1982
DOI:https://doi.org/10.1103/PhysRevC.26.1531
©1982 American Physical Society