Mass distributions for thermal-neutron-induced fission ($n, f$) of ${}_{}{}^{255}{}_{}{}^{}\mathrm{Fm}$ and ${}_{}{}^{251}{}_{}{}^{}\mathrm{Cf}$ have been determined radiochemically. Both mass distributions are asymmetric with a peak-to-valley ratio of about 2.6 for ${}_{}{}^{255}{}_{}{}^{}\mathrm{Fm}$ and about 13 for ${}_{}{}^{251}{}_{}{}^{}\mathrm{Cf}$. Cross sections were determined to be 3200±320 b for ${}_{}{}^{255}{}_{}{}^{}\mathrm{Fm}(n, f)$ and 5300±530 b for ${}_{}{}^{251}{}_{}{}^{}\mathrm{Cf}(n, f)$.

NUCLEAR REACTIONS, FISSION ${}_{}{}^{255}{}_{}{}^{}\mathrm{Fm}(n, f)$, ${}_{}{}^{251}{}_{}{}^{}\mathrm{Cf}(n, f)$, $E=0.025\mathrm{}$ eV; measured radiochemical mass yields and ${\sigma }_f$.

• Received 6 January 1975

DOI:https://doi.org/10.1103/PhysRevC.11.1676