Neutron capture mechanisms in the threshold region

Neutron capture mechanisms in the threshold region are investigated through the measurement of high resolution y-ray spectra and resonance capture cross sections. Initial and final state width correlations are observed for many nuclides across the periodic table, and are indicative of dominant valence and doorway interactions. A detailed investigation of resonant capture in the isotopes of iron provides strong evidence for these effects. Estimates of the magnitude of the doorway component are obtained for the 3s region when valence and statistical contributions are compared with the average s- and p-wave radiative widths.