Interaction of laser radiation with free atoms

Abstract

The review describes and interprets the basic phenomena recently observed in the interaction between free atoms and laser radiation. Some of these have been known for a long time in magnetic resonance but in the optical range, the situation is strongly modified because of spontaneous emission and the Doppler effect. Therefore, particular attention is paid to resonance fluorescence and Doppler-free spectroscopy but without dwelling on applications. Transient effects are also discussed, but all the phenomena which characterize, not specifically the interaction between atoms and fields, but the free evolution of atoms after coherent excitation are ignored. Pulse propagation experiments are described in detail and multiphoton processes are considered, with special emphasis on Doppler-free multiphoton excitation and resonant multiphoton ionization.