Photoejection of High-Energy Nucleons from Nuclei and the Quasi-Deuteron Model. I. Cross Sections and Angular Distributions

Abstract

Experiments are described on the photoproduction of high energy neutron-proton pairs from complex nuclei. The results provide further confirmation and some clarification of the quasideuteron model of Levinger.In these experiments targets of D, Li, and O are bombarded by a 340-Mev bremsstrahlung beam. In one set of measurements, intended to check the kinematical features of the model, we have observed the angular spread of the $n\ensuremath{-}p$ coincidences which arises from the momentum distribution of nucleons in the complex nuclei. These observations were preliminary to the main group of measurements, which consisted in a direct comparison of the cross sections and angular distributions of quasi-deuteron disintegrations for Li and O to those from D for 260-Mev photons. (A more limited group of measurements are reported for 200-Mev photons.)The results of these observations indicate that the quasideuteron photodisintegration proceeds through the same mechanisms as are responsible for the photodisintegrations of free deuterons at the energies investigated. However, a quantitative understanding of the data, especially for the cross-section ratios, required an analysis of the effects of scattering of the emerging nucleons in the target nuclei. Qualitative arguments concerning these effects are given herein; the more quantitative discussion is postponed to a future communication.