Average Radiative Capture Cross Sections for 7- to 170-kev Neutrons

Abstract

Measurements of neutron radiative capture cross sections in the kev region have been made using fast (millimicrosecond) time-of-flight techniques and a large liquid scintillator tank. Two series of measurements have been completed on a number of nuclides. These are determinations of (1) cross sections relative to that of indium at 30 kev and at 65 kev for 49 elements, and (2) cross sections as a function of neutron energy for the following nuclei: Br, Nb, Pd, Ag, Cd, In, Sb, I, Pr, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ta, W, Pt, and Au. Curve fits, using the statistical model, have been obtained for Br, Nb, Ag, In, Sb, I, Pr, Tb, Ho, Tm, Lu, Ta, and Au. The results demonstrate the presence of the $2p$ giant resonance near $A=100$ predicted by the optical model. The average nuclear parameters obtained are in good agreement with recent low-energy total cross-section results, but are in poor agreement with earlier results. Possible reasons for these disagreements are discussed.