Nuclear physics
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Nuclear physics is the branch of physics concerned with the nucleus of the atom. It has three main aspects: probing the fundamental particles (protons and neutrons) and their interactions, classifying and interpreting the properties of nuclei, and providing technological advances.
Forces
Nuclei are bound together by the strong force. The strong force acts over a very short range and causes an attraction between nucleons (protons and neutrons). The strong nuclear force is so named because it is significantly larger in magnitude than the three other fundamental forces (weak, electromagnetic and gravitational). The strong force is highly attractive at only very small distances which, combined with repulsion between protons due to the electromagnetic force, allows the nucleus to be stable. The strong force felt between nucleons arises due to the exchange of gluons. The study of the strong force is dealt with by quantum chromodynamics (QCD).
Nuclear models
Nucleons in the nucleus move about in a potential energy well which they themselves create arising from their interaction with, and movement with respect to, each other. Nucleons can interact with each other via 2-body, 3-body or multiple-body forces. The fact that many nucleons interact with each other in a complicated way makes the nuclear many-body problem difficult to solve.
There broadly exists two types of nuclear models which attempt to predict and understand characteristics of nuclei. These are microscopic and macroscopic nuclear models. Microscopic nuclear models approximate the potential which the nucleons create in the nucleus. Individual interactions are combined as linear sums of potentials. Almost all models use a central potential plus a spin orbit potential. The difference between models is then defined by the 3-body potential used, and/or the shape of the central potential. The form of this potential is then inserted into the Schrodinger equation. Solution of the Schrodinger equation then yields the nuclear wavefunction, spin, parity and excitation energy of individual levels. The form of the potential used to determine these nuclear properties indicates the type of microscopic model. The shell model and deformed shell model (Nilsson model) are two examples of microscopic nuclear models.
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