ABSTRACT
A toms are the building blocks of matter. But they serve an even more important role in atomic physics since they are not only objects to study
and understand as deeply as possible, but also in the words of I. I. Rabi, “Nature’s laboratory,” where you can study the interaction of electrons and nucleus, the interaction of matter and radiation, or very weak interactions (e.g. parity or time-reversal symmetry violation) with exquisite precision. In this chapter, we shall use the phrase “one-electron atom” to include not only atoms which are iso-electronic with hydrogen (such as He+, Li++, etc.), but also atoms with one-electron which is far less weakly bound than all the others so that the inner electrons may be considered collectively as a core whose interaction with the active electron may be adequately described by parameters such as scattering length, polarizability, etc.
