Neutron Resonance Parameters and Transmission Measurements inU235

Transmission measurements have been made for ${\mathrm{U}}^{235}$ with a resolution of 0.05 to 0.07 μsec/meter using the Materials Testing Reactor fast chopper, and resonances have been studied below 60 ev. Breit-Wigner parameters have been obtained for more than 40 resonances. Four new resonances have been found at 12.8, 28.6, 29.9, and 34.7 ev. The 25.7-ev resonance previously reported has been split into two resonances, 25.6 and 25.9 ev. The ratio of $\frac{{{\overline{\Gamma }}_n}^0}{D}$ for resonances below 50 ev was found to be 1.0±0.2×${10}^{-4\mathrm{}}$. The level spacing of 1.40±0.15 ev is one of the smallest so far observed. Data on the distributions of ${{\Gamma }_n}^0$ are presented.