Angular Distribution of Neutrons Scattered from Cadmium, Tin, and Bismuth

The differential cross sections for the scattering of 3.7-Mev neutrons from cadmium, tin, and bismuth have been measured over an angular range between 13 degrees and 140 degrees with an angular resolution of about \ifmmode\pm\else\textpm\fi{}10 degrees. The effects due to higher-order scattering have been removed at each measured angle by extrapolation. Previous measurements of the differential cross sections of aluminum, iron, and lead gave a uniform shift of the position of the first minima in the curve with atomic weight. In the present measurements, the curves for cadmium and tin, while quite similar, do not fall uniformly between those of iron and lead. The curve for bismuth, however, is again quite similar to that for lead. Possible explanations of this behavior are discussed in light of the continuum theory of nuclear reactions.