Studies of shapes and stability in exotic nuclei

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The shape of an atomic nucleus is one of its most fundamental properties. The simplest shape that a nucleus can have is a sphere. Nuclei that have closed shells of neutrons and protons are spherical. Away from closed shells, nuclei can become non-spherical, or deformed. The most common deformed shapes are rugby-ball (prolate) shapes or pumpkin (oblate) shapes, both of which are termed quadrupole deformation. Some nuclei can take on a reflection-asymmetric pear shape, termed as octupole deformation while some others can take a shape of a spinning top, termed as hexadecapole deformation. In a quantum-mechanical system of particles, the emergence of a shape is a direct consequence of the interaction between the constituent particles. Therefore, shape studies of nuclei can probe nucleon-nucleon interactions and, in particular, neutron-proton interactions, which are yet to be fully understood. The nuclear shape can also affect the characteristics of particle and cluster decays, which are currently topics at the forefront of nuclear-structure physics, particularly in the regions at the limits of stability. Experimental studies that are focused on the measurement of nuclear deformations will allow a comparison of the measured shapes with those predicted by theoretical calculations to test the validity of models. In general, the shapes of nuclei indisputably have an important impact on several areas of nuclear physics and some other areas such as the origin of elements in astrophysical environments. Consequently, the proposed experimental studies of shapes, neutron-proton interactions and particle decays are at the forefront of current nuclear-physics research.