Luminescence

Luminescence - cold light bodies, not related to them by heating to high temperatures. Luminescence can be caused by the action on the body of light (photoluminescence), the flow of electrons (cathodoluminescence), the energy of chemical reactions (chemiluminescence method) and other Illumination of some bacteria, fish, insects called bioluminescence. Luminescence, disappearing simultaneously with the termination of excitation phosphor (substances that luminesce), called fluorescence, and lasting for an appreciable period of time after the termination of excitation - the phosphorescence. Cm. also Luminescent analysis, fluorescence microscopy.

Luminescence (from lat. lumen, luminis - radiation, light) - excessive radiation substances in excess of its normal at a given temperature of thermal radiation and duration longer than the period of oscillations of light waves. The reason luminescence is any impact on the substance, leading to the transition of molecules in the excited state. Part of the absorbed when this substance energy is released then as energy fluorescent glow (this part, expressed as a percentage, called the energy yield of luminescence). By the method of excitation of luminescence is divided into photoluminescence (excited by light), the chemiluminescence (excited by the energy exogenous chemical reactions; special case it is bioluminescence, for example, the glow of fireflies). In addition, a well-known roentgenofluorescence, radioluminescence, cathodoluminescence, electroluminescence. Duration of the luminescence divided into fluorescence, which glow lasts until almost operates a stimulating effect, and happened as the glow continues even after the termination of the exciting effects.
Property luminesce can possess solid, liquid and gaseous substances. Under the action of invisible ultraviolet radiation photoluminescent many substances giving ultraviolet or visible glow in different colors. Under the effect of visible light, mostly purple, blue and green, can significantly photoluminescent only some classes of compounds. These include aromatic compounds with double paired relationships, dyes, porphyrins and their derivatives. Property luminescence is used in fluorescent analysis (see).
Glow in the photoluminescence can be observed, as shown in the figure. If instead the eye of the observer to install a solar cell power, you get fluorimeter. Fluorimeter suitable for the quantitative determination of concentration lyuminestsiruyushchikh substances in solution or in a transparent solid phase in the absorption of the exciting light L. no more than 20 - 30%.
Light luminescence can be expanded in range, which, as absorption spectrum is determined by molecular structure of substances. Registration of spectra of L. is spectrofluorimetry. The spectra gases usually linear and complex compounds in solution or in the solid state is wide washed or strip), which is offset in the long-wavelength part of the spectrum with respect to the absorption band. The intensity L. might be negatively affected and even fall to zero when added to the solution or suspension, which contain fluorescent substance, some compounds-extinguishers, because of the interaction of molecules of tusitala with molecules lyuminestsiruyushchikh substances as a result of either collisions, or education systems. The transition lyuminestsiruyushchikh connection in the aggregated state (in concentrated solutions or multicomponent biological objects) significantly changes all luminescence characteristics of the substance. HP has practical application in production, physics, chemistry, Geology, biology, forensic, medicine and food industry.

Photoluminescence (acquisition scheme); 1 - the exciting light source; 2 - the eye of the observer; 3 - a filter that only passes light, exciting luminescence; 4 - transparent filter only for the light of luminescence; 5 and 6 lenses; 7 - fluorescence object.