ABSTRACT
I n the previous chapter, we have discussed atoms as if the nuclei were point charges with no structure and infinite mass. Real nuclei have mass, pos-
sibly non-zero angular momentum ~I, and a charge which is spread out over a finite volume. As a result, they possess a magnetic dipole moment and an electric quadrupole moment coupled to the electronic angular momentum, and possibly higher moments as well. All of these properties affect the atomic energy levels, at a level about 10−5 Ry-these effects will be discussed in this chapter.
