A study of the charged particles emitted from certain fast-neutron induced reactions

Abstract

The models which have been used to explain the observed features of nuclear reactions have had a chequered history of waxing and waning popularity. Nearly three decades ago it was suggested that single particle direct interactions might prove a satisfactory basis for a model of nuclear reactions; however, the theory was discarded when the discovery of narrow resonance structure in reaction cross-sections forced the adoption of the compound nucleus model. Over the years, this compound nucleus model has played an important part in predicting the details of reactions going through discrete states and has been extended to include the cases where the compound nucleus has available a statistically large number of overlapping levels. Notwithstanding the successes of the compound nucleus model, direct interaction theory had a revival early in the last decade when examinations of the details of many reactions showed features which were foreign to the decay of compound nuclei. These investigations, which gave widespread support to the theory of direct interactions, raised many doubts about the usefulness of the statistical model and caused extensive discrediting of this part of compound nucleus theory. Today, however, it appears likely that the two models are reconcilable and can exist side by side. It has been suggested that direct interactions and evaporation processes can be simultaneously present in many nuclear reactions and are extreme models for the fast and slow components of nuclear interactions. (First two paragraphs of introduction.)