The total cross sections of Li, Be, ${\mathrm{B}}^{10}$, B, C, and O were measured for neutrons of energies between 1 and 3.3 Mev. Neutrons of about 20-kev energy spread were produced by bombarding a thin layer of Zr in which tritium had been absorbed with protons from the electrostatic generator. Resonances were observed in all nuclei except Li. In addition to well-defined levels, evidence was found for slow variations of the cross sections with energy which might be explained by the presence of very wide levels in all these elements.

• Received 11 June 1951

DOI:https://doi.org/10.1103/PhysRev.84.69