Collective Nuclear Excitations Probed with Neutrons and Nuclear Astrophysics

核科学小组利用肯塔基大学范德格拉夫加速器实验室进行的拟议研究将集中在核结构、中子反应和散射以及核天体物理等相关主题上。原子核结构的研究主要面向a)探索低激发能下的集体多声子激发，如四极-四极、四极-八极和八极-八极模，b)定义形变和过渡核中混合对称或“剪刀模”激发的性质，C)确定质子和中子在集体模式中的单独作用，以及d)了解核壳结构和核形状转变的性质。由于需要跃迁率来解释这些现象，我们实验室开发的用非弹性中子散射后的多普勒频移衰减法测量核能级寿命的技术对这些研究至关重要。中子散射研究将集中于了解中子探测的激发与其他强子或轻子探测的激发之间的差异，并将补充许多其他正在进行的核结构研究。将继续详细研究束缚态区的核能级密度以及能级密度的能量依赖性。建议进行精心挑选的、特别适合我们的能力和设施的核天体物理学研究。

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.