Fragment-Mass and Kinetic-Energy Distributions from the Spontaneous Fission ofCm246

Abstract

Energies of coincident fission fragments from a thin, spontaneously fissioning ${}_{}{}^{246}{}_{}{}^{}\mathrm{Cm}$ source were measured with silicon surface-barrier detectors. Pre-neutron-emission mass and total-kinetic-energy distributions were deduced from the data. The average pre-neutron-emission fragment total kinetic energy ${\overline{E}}_K$ was found to be 184.2 MeV, in agreement with ${}_{}{}^{245}{}_{}{}^{}\mathrm{Cm}$ ($n,f$) results. The mass distribution has a peak-to-valley ratio of 142, and is similar to those from other spontaneously fissioning nuclei. Fine structure in the mass distributions from ${}_{}{}^{245}{}_{}{}^{}\mathrm{Cm}\mathrm{}(n,f)\mathrm{}$, ${}_{}{}^{246}{}_{}{}^{}\mathrm{Cm}\mathrm{}\left(\mathrm{sf}\right)\mathrm{}$, and ${}_{}{}^{250}{}_{}{}^{}\mathrm{Cm}\mathrm{}\left(\mathrm{sf}\right)\mathrm{}$ appears to be associated with fragments of mass $\approx 144$ amu. Predictions for ${\overline{E}}_K$ from fission systematics were not found to describe adequately the observed ${\overline{E}}_K$ values for the spontaneous fission of Cm isotopes.