Coupled-channels Neutron Reactions
LLNL, Nuclear Theory and Modeling Group
Micoscopic calculations of reaction cross sections for nucleuon-nucleus scattering have been performed by explicitly coupling the elastic channel to all of the particle-hole (p-h) excitation states in the target and to all the relevant pick-up chanels. Coupling between inelastic states were found to be not significant, while inclusion of coupling to pick-up channels was an important contribution to the absorption. For the first time, calculations of excitations account for all of the observed reaction cross-sections, for incident energies above 10 MeV. These channel couplings should generate all of the imaginary components of the neutron optical potential, which summarizes the overall effects of non-elastic channels on the elastic wave functions. We also investigate neutron reactions on strongly deformed nuclei in the actenide region. Focus is on the convergence of the compound-nucleus production cross section (also called the fusion and the absorption cross section), because this is the total of the inelastic, gamma, and fission cross sections needed for Hauser-Feshbach calculations.