ABSTRACT
This chapter provides an overview of the energy distribution of the beta strength, and a detailed description of possible quantitative microscopic treatments. It is concerned with the matrix elements for allowed transitions. The chapter considers the simple structure of Fermi transitions. These may be calculated practically independently of the details of the nuclear structure. In beta decay a neutron–hole proton or proton–hole neutron excitation is generated. The excitation energy relative to the ground state is then for n-particle–n-hole states simply given by the sum of the energies of the particle orbitals minus the sum of the energies of the hole orbitals. In the pairing model, as well as the movement of the nucleons in a mean potential, the so-called pairing forces is also considered. According to the independent nucleon model and also to the pairing model, the strength of the Gamow–Teller transitions should be more or less independent of the energetic position of the final state in the daughter nucleus.
