The scientific study of the forces, reactions, and internal structures of atomic nuclei. the area of physics which is concerned with the structure and features of the nucleus (=central part) of atoms. Branch of physics dealing with the structure of the atomic nucleus and radiation from unstable nuclei. A principal research tool of nuclear physics is a high-energy beam of particles, such as protons or electrons, directed as projectiles against nuclear targets. By analyzing the directions and energies of the recoiling particles and any resulting nuclear fragments, nuclear physicists can obtain details of nuclear structure, the strong force that binds nuclear components together, and the release of energy from the nucleus