Theory of atomic spectra

After reviewing the various processes by which radiation interacts with matter, we'll examine optical and X-ray spectra in turn, starting with the simplest spectrum, that of the hydrogen atom.

As we shall see, atomic spectroscopy has provided us with extremely precise knowledge of the external electronic configurations of atoms, which are highly varied and determine the chemical properties of the elements. X-ray spectra, for their part, reflect the internal electronic configurations of atoms; we shall see, among other results, that their characteristic shape is direct evidence of the arrangement of these electrons in successive layers.

The study of molecular spectra is the subject of article P 2 656.