Fission Cross Section ofU235

Abstract

The fission cross section of ${\mathrm{U}}^{235}$ has been investigated with high resolution between 0.03 and 60 eV using the neutron time-of-flight facility at the Livermore linear electron accelerator. Normalization of the relative cross sections in the thermal region indicates that the fission cross sections generally accepted are about 20% too large in the region between 5 and 60 eV. Values for ${\sigma }_0{\Gamma }_f$ and ${\Gamma }_f$ above 5 eV are compiled and are compared with similar measurements by other investigators. Evidence is also presented which indicates that the fission widths fall into two groups probably related to the two total angular momenta involved in the reaction.