Collective Nuclear Excitations Probed with Neutrons and Nuclear Astrophysics

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The proposed research of the nuclear science group using the Van de Graaff accelerator laboratory at the University of Kentucky will focus on related topics in nuclear structure, neutron reactions and scattering, and nuclear astrophysics. Studies of nuclear structure are primarily oriented toward a) exploring collective multi-phonon excitations, such as quadrupole- quadrupole, quadrupole-octupole, and octupole-octupole modes, at low excitation energies, b) defining the nature of mixed-symmetry or "scissors mode" excitations in deformed and transitional nuclei, c) defining the separate roles of protons and neutrons in collective modes, and d) understanding nuclear shell structure and the nature of nuclear shape transitions. Since transition rates are required to interpret these phenomena, the techniques developed in our laboratory to measure nuclear level lifetimes with the Doppler-shift attenuation method following inelastic neutron scattering are crucial to these investigations. Neutron scattering studies will concentrate on understanding the differences between excitations probed by neutrons and by other hadrons or leptons and will complement many other ongoing nuclear structure investigations. Detailed studies or nuclear level densities in the bound state region and the energy dependence of level densities will be pursued. Carefully selected studies in nuclear astrophysics that are particularly appropriate to our capabilities and facilities are proposed.