Elementary radiative processes

In this introductory chapter, we consider the elementary radiative processes for both free atomic particles (atoms, ions, and molecules) and particles interacting with a monochromatic laser field. For more advanced considerations, the reader is advised to refer to the classical textbooks (Loudon 1973 Sargent et al. 1974 AUen and Eberly 1975 Sobelman 1979 Haken 1981 Knight and Allen 1983 Meystre and Sargent 1990 Cohen-Tannoudji et al. 1992 Foot 2004). Extensions of this material are treated in subsequent chapters, wherein various light field configurations, atomic particles, and the processes of interaction between atomic particles and laser fields are considered in detail. 

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When considering the conditions of equilibrium between atomic particles and thermal radiation (black-body radiation), Einstein introduced another two elementary radiative processes whose rate depended on the radiation intensity. This was a... 

In the previous sections we considered the processes of non-radiative electron tunneling. Along with them, processes are possible when, in the course of one elementary act, the electron tunnels from a donor to an acceptor and simultaneously radiates a quantum of light [7]. Using the... 

The results of experimental research have also stimulated the appearance of theoretical papers devoted to the analysis of an elementary act of electron tunneling reactions in terms of the theory of non-radiative electron transitions in condensed media and to the derivation of the kinetic equations of long-range electron transfer processes [19-30],... 

The photochemistry of the substituted stUbenes opens up a unique possibility to follow the different timescale processes (in the femto-, pico-, and nanosecond regions) occurring in the molecules after irradiation. The investigated processes are the electronic polarization, vibrational and polar relaxation, radiative and non-radiative decay of the excited state, and twisting transition in the excited state. All these processes take place in the elementary act of a chemical reaction, but these are overlapped by each other and thus are undetectable by direct experimental measurements. It means that it is practically impossible to elucidate and differentiate the contribution of such factors as substituent or solvent effects to the above-mentioned processes. However, a Hammett-like correlation approach in photochemistry allowed one to elucidate and differentiate the contribution of these factors. 

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