Spins and Electromagnetic Moments of Nuclei

Abstract

Atomic nuclei are quantum objects at the heart of an atom, immersed inside the electron cloud. The number of protons in the nucleus, Z, defines the element. Nuclei with the same number of protons and a different number of neutrons, N, are called isotopes of a specific element. Nuclei can have a spin, a magnetic dipole moment, and an electric quadrupole moment. These fundamental properties provide detailed information about the nuclear wave function and are therefore excellent probes to study how the quantum structure of isotopes evolves as a function of N, Z, and excitation energy. The magnetic dipole and electric quadrupole moments in odd-even or odd-odd isotopes can be measured in their ground state or for isomers with half-lives ranging from a few nanoseconds up to stability, using a variety of experimental techniques. These observables can also be calculated using a variety of nuclear models, which in turn can then be tested using the measured electromagnetic moments. This chapter will introduce the formal description of nuclear magnetic dipole and electric quadrupole moments, supplemented with examples to provide an insight into what information they convey about the nuclear wave function, and how they can be used to test modern nuclear theories. Particular attention is given to the interpretation of the moments in the shell-model picture.