Distribution of Mass in the Spontaneous Fission ofFm256

Abstract

The distribution of mass in the spontaneous fission of ${}_{}{}^{256}{}_{}{}^{}\mathrm{Fm}$ has been investigated by the radiochemical determination of the fission yields for 28 mass chains. The mass distribution is asymmetric with a peak-to-valley ratio of ∼12. The average masses of the light and heavy groups are 111.9 and 141.0, respectively. The fission-yield data indicate a value of 3 ± 1 for $\overline{\nu }$, the average number of neutrons emitted per fission. A comparison of the characteristics of the mass distribution for low-energy fission of nuclides ranging from ${}_{}{}^{227}{}_{}{}^{}\mathrm{Th}$ to ${}_{}{}^{256}{}_{}{}^{}\mathrm{Fm}$ is given.