Neutron Elastic Scattering in the Energy Region 1.5 to 4.0 MeV for Radiogenic Lead and Bismuth

摘要

Elastic scattering of 1.5 to 4.0 MeV neutrons from radiogenic lead, Pb sub (r), and exp 209 Bi has been measured using a time-of-flight technique. The experimental results show the existence of a b broad maximun in the angle integrated elastic cross section centered at a neutron energy of about 3 MeV for both elements. Further, this cross-section maximum is more pronounced for exp 209 Bi than for Pb sub (r). The data were analysed in terms of an optical model potential with spherical symmetry. The energy dependence of the total shape elastic cross sections calculated for Pb sub (r) and exp 209 Bi from this model shows only minor differences, which are caused by the small mass difference and the fact that nuclear structure effects are not taken into account in the optical model. The observed cross section differences between Pb sub (r) and exp 209 Bi have been explained as a compound nucleus effect caused by the essentially larger ground state spin of exp 209 Bi as compared to Pb sub (r). Different formalisms have been used to correct the calculated compound elastic cross sections for level width fluctuations. (Atomindex citation 14:718172)