Luminescence, matter/radiation interaction

The physical basis of spectroscopy is the interaction of light with matter. The main types of interaction of electromagnetic radiation with matter are absorption, reflection, excitation-emission (fluorescence, phosphorescence, luminescence), scattering, diffraction, and photochemical reaction (absorbance and bond breaking). Radiation damage may occur. Traditionally, spectroscopy is the measurement of light intensity... 

As pointed out by Dexter (41), the over-all theoretical problems of luminescence are exceedingly difficult to treat even in their simplest forms. This is true not only because they involve simultaneous interactions among radiation, matter, and phonons, but also because the specific details of the wave functions are of first-order importance. 

Abstract Photochemistry is concerned with the interaction between light and matter. The present chapter outlines the basic concepts of photochemistry in order to provide a foundation for the various aspects of environmental photochemistry explored later in the book. Electronically excited states are produced by the absorption of radiation in the visible and ultraviolet regions of the spectrum. The excited states that can be produced depend on the electronic structure of the absorbing species. Excited molecules can suffer a variety of fates together, these fates make up the various aspects of photochemistry. They include dissociation, ionization and isomerization emission of luminescent radiation as fluorescence or phosphorescence and transfer of energy by intramolecular processes to generate electronic states different from those first excited, or by intermo-lecular processes to produce electronically excited states of molecules chemically different from those in which the absorption first occurred. Each of these processes is described in the chapter, and the ideas of quantum yields and photonic efficiencies are introduced to provide a quantitative expression of their relative contributions. 

Resonant interactions are ordinarily much stronger than non-resonant ones. Each characteristic frequency is actually a band of frequencies of width Av more or less symmetrically distributed around the same center vq. The resonant transfer of energy from a radiation field to matter is called absorption. The absorption process ereates also an induced dipole moment, but a larger one than in the case of polarization. The transfer of energy from matter to the radiation field is termed emission (or luminescence). We... 

As mentioned, the most attractive properties of these systems used in their applications originate from the electric dipole/ <—> / transitions. They might be direct and observed as absorption or emission, or play a role as initial and final steps of sensitized luminescence, for example. In all of these cases the amplitude of the electric dipole transition is determined by the certain order of the time-dependent perturbation theory applied for the description of the interaction between matter and the radiation field. Each order of the perturbing expansion... 

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