Quantum Description of the Matter-Radiation Interaction

Quantum physics describes the radiation field, matter systems (like atoms, molecules and solids) and their interactions. The processes of interaction consist of absorption, emission and diffusion of photons, the basis of many experimental techniques to study materials and their electronic properties. The states of the electron systems can be studied in a single-particle picture or in a many-electron scheme; the two approaches will be compared in the study of the elementary processes of interaction with light at different levels of approximation for the initial, final and intermediate states of the matter system.