Expressions very similar to the "Breit-Wigner" formulas are derived for the scattering and absorption cross section of nuclear particles, e.g. neutrons, protons, etc. The resonance energies, particle widths and other characteristic features can be expressed in terms of the logarithmic derivative of the particle wave function at the nuclear surface. Simple assumptions about the behavior of the incident particle inside the nucleus are used to find approximate expressions for (1) the particle widths in terms of the level spacing; (2) the neutron scattering cross section near and between resonances; (3) the total cross section and the absorption cross section averaged over neighboring levels for neutron energies up to 1 Mev. These results are then compared with the experimental data and are found to be in qualitative agreement.

• Received 5 August 1946

DOI:https://doi.org/10.1103/PhysRev.71.145