Quenching of Luminescence

a decrease in luminescence efficiency owing to various causes.

Quenching of luminescence may occur when impurities are added to a phosphor, when the concentration of the luminescent substance is increased (concentration quenching), when the luminescent substance is heated, or when the substance is exposed to infrared radiation or an electric field. As a result of such causes, the probability of nonradiative transitions of the luminescent molecules from the excited state to the ground state increases in comparison with the probability of radiative transitions (seeQUANTUM TRANSITIONS). In the case of the recombination luminescence of crystal phosphors, quenching of luminescence is due to nonradiative recombination of charge carriers with quenching centers, which may be crystal defects or impurity atoms.

Quenching of luminescence is usually undesirable, and very high requirements are therefore imposed on the purity of luminescent substances. Special types of phosphors, in which rapid quenching of luminescence occurs when the temperature increases or when the phosphor is exposed to infrared radiation, are used, however, as sensitive indicators of long-wave radiation (seeRADIATION DETECTOR).