Nuclear Shell Structure

There is convincing evidence from the study of nuclear stabilities, magnetic moments, spins, and from other sources, that there is a marked regularity of nuclear properties, particularly clearly shown by breaks at 2, 8, 20, 28, 50, 82 and 126 protons or neutrons. This is explained in terms of an individual level model of nuclear structure similar to the model used in explaining the periodicity of atomic structure. In nuclei, a strong spin-orbit interaction, of unexplained origin, plays an important part. This model leads to an excellent understanding of nuclear regularities, particularly of spins and magnetic moments. It has severe limitations, however, and, particularly when large shells are filling, it needs to be supplemented by a more `collective' approach to nuclear structure.