Fluorescence theory emission

The theory for the time course of phosphorescent or fluorescent light emission was described by Stern and Volmer [7]. The relationship is given by... 

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X-Ray Fluorescence Theory Wavelength Dispersive X-Ray Fluorescence Energy Dispersive X-Ray Fluorescence Total Reflection X-Ray Fluorescence Particle-Induced X-Ray Emission Synchrotron X-Ray Fluorescence... 

See also Atomic Absorption, Methods and Instrumentation Atomic Fluorescence, Methods and Instrumentation Fluorescence and Emission Spectroscopy, Theory. 

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Though theories have been proposed (32-35) to explain this phenomenon, the mechanism of fluorescence is still not yet fully understood. Jankow and Willis (36) proposed a mechanism which involves a direct excitation of the molecule or an impurity to an excited state, followed by internal conversion and then reversion back to the original state with emission of light. This mechanism can be explained as follows A molecule in the lowest vibrational level of the ground state A is transferred to a certain vibrational level in the excited state D. The molecule tends to cascade into the lowest vibrational level of state D by collisions with other excited molecules. It passes from state D to state C and then to state B by radiationless transi-... 

Jablonski (48-49) developed a theory in 1935 in which he presented the now standard Jablonski diagram" of singlet and triplet state energy levels that is used to explain excitation and emission processes in luminescence. He also related the fluorescence lifetimes of the perpendicular and parallel polarization components of emission to the fluorophore emission lifetime and rate of rotation. In the same year, Szymanowski (50) measured apparent lifetimes for the perpendicular and parallel polarization components of fluorescein in viscous solutions with a phase fluorometer. It was shown later by Spencer and Weber (51) that phase shift methods do not give correct values for polarized lifetimes because the theory does not include the dependence on modulation frequency. 

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