Quenching Correction in Liquid Scintillation Counting
Two types of quenching are encountered in liquid scintillation counting, chemical and color quenching. Chemical quenching is caused by the presence of nonfluorescent molecules in the liquid scintillator system which interfere with the energy transfer between the solvent and the organic scintillator. In a scintillation solution, the radiation energy from a radioactive sample is expended in inducing molecular excitation of the solvent molecule. This excitation energy is transferred, according to Kallman and coworkers , by a process of diffusion, migration, or single-step jump to the solute molecule. If the solute molecules are those of an organic scintillator, they will be excited and then de-excited, with emission of photons which can be detected by a photomultiplier tube and counted. If the solute molecules are those of a nonfluorescent compound, they will be excited, but de-excitation occurs by radiationless transition without concomitant emission of photons. This thermal degradation of radiation energy without enhancing the fluorescence yield of the liquid scintillator system is the cause of chemical quenching.
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