The interaction of electromagnetic radiation with one-electron atoms

We examine the interactions of radiation with a hydrogen-like atom as a simple example that displays many of the typical characteristics of how atoms and molecules in general interact with photons. We will examine the spectral line processes of absorption, stimulated emission (emission caused by passing radiation), spontaneous emission (radiation without any external stimulus), and the continuum process of photoelectric absorption. In principle these processes should be described using quantum electrodynamics. However, this course is not at that level. We will describe the radiation ̄eld semiclassically (so we will have to study spontaneous emission using a statistical argument of Einstein), but use a quantum mechanical description of the atoms.