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 state

• 2. Magnetic dipole moments μ as summarized in Schmidt diagrams

• 3. Electrical quadrupole moments Q

• 4. Existence of isomers and the occurrence of islands of isomerism

• 5. Parity of nuclear levels

• 6. Discontinuities of nuclear binding energy for certain values of N or Z

• 7. Substantially constant density of nuclei

• 8. Dependence of the neutron excess (N–Z) on A ^5/3 for stable nuclides

• 9. Approximate constancy of the binding energy per nucleon B/A

• 10. Fission by thermal neutrons of ²³⁵U and other odd nuclides

• 11. Nonexistence in nature of nuclides heavier than ²³⁸U

• 12. Wide spacing of low-lying excited levels in nuclei, in contrast with the close spacing of highly excited levels

• 13. Existence of resonance-capture reactions.