Atoms in a strong radiation field are interesting objects. While, for a long time, first-order perturbation theory was adequate to explain low-intensity effects, the development of the pulsed laser has changed matters dramatically, allowing fields to be applied that have a large, or even dominant influence on atomic structure: super-intense fields.
The term is actually quite difficult to define, however, and it has no absolute meaning. An atom in a radiation field can best be described in terms of the ratios of the quantities involved. In almost all cases, however, quiver motion is the dominant feature of all atomic physics in the super-intense regime. But this can result in a wide variety of phenomena, such as ionization, emission of radiation, exchange of excess photons with the field, double ionization, etc. All of these aspects are discussed in the present book, grouped under four main headings: Multiphoton ionization; Multielectron atoms; Hard radiation quanta; and Coherence and interference.