Slow Neutron Resonance Spectroscopy. I.U238

The results of time-of-flight measurements of ${\mathrm{U}}^{238}$ resonances in the region 90-1300 ev are presented and resonance parameters for levels up to 1000 ev are obtained. Neutron widths for the 55 observed levels and radiation widths for 32 of the stronger levels are deduced. The deduced neutron width distribution is found to be in good agreement with the theoretical prediction of Porter and Thomas for a single channel process, while the level spacing distribution agrees with the "repulsion" formula suggested by Wigner. The average value of the radiation widths was found to be (24.6±0.8)×${10}^{-3\mathrm{}}$ ev, while the average reduced neutron width and level spacing were found to be (1.76±0.26)×${10}^{-3\mathrm{}}$ ev and 18.5±1.3 ev, respectively. These values are in good agreement with earlier results reported by other workers. A strength function of (0.95±0.15)×${10}^{-4\mathrm{}}$ is obtained.