Nuclear Models

Abstract

The models used in nuclear physics as well as in atomic physics are invented because we do not know how to solve the many-body Schrodinger equation either with Coulomb forces or nuclear forces. The observed features of light and heavy nuclei are too complex to be explained by a reliable theory. In the absence of an exact theory, a number of nuclear models have been developed. These are based on different sets of simplifying assumptions. Each model is capable of explaining only a part of our experimental knowledge about nuclei. The experimental facts which are to be explained by a model are: 1.Nuclear Spins I of ground state2.Magnetic dipole moments μ as summarized in Schmidt diagrams3.Electrical quadrupole moments Q4.Existence of isomers and the occurrence of islands of isomerism5.Parity of nuclear levels6.Discontinuities of nuclear binding energy for certain values of N or Z7.Substantially constant density of nuclei8.Dependence of the neutron excess (N–Z) on A5/3 for stable nuclides9.Approximate constancy of the binding energy per nucleon B/A10.Fission by thermal neutrons of 235U and other odd nuclides11.Nonexistence in nature of nuclides heavier than 238U12.Wide spacing of low-lying excited levels in nuclei, in contrast with the close spacing of highly excited levels13.Existence of resonance-capture reactions.