Kinetics of Photosensitized Reactions

When a photosensitizer is involved in the photoreaction, i.e., the absorbing substance transfers the energy to another nonabsorbing molecule that then undergoes reaction, the above principles still apply, with the analysis applied to the acceptor 

A perfect photosensitizer will not be transformed in the photosensitizing process, although in reality, some degradation of the photosensitizer will occur in time. Nonetheless, the rate of the photosensitized reaction will depend directly on the sensitizer concentration at low values where not all of the relevant incident radiation is being absorbed. Most studies of this type of photoreaction use a high concentration of the acceptor A, in which case the transformation of A will follow apparent zero-order kinetics. 

APPLICATION OF KINETIC MEASUREMENTS TO REACTION MECHANISM DETERMINATION IN PHOTOSTABILITY 

Rate measurements are an integral component of mechanism determination in photochemical reactions. Although the values of rate constants are specific to the particular apparatus used, as emphasized in Section Reaction Kinetics and Photostability, the comparison of rates obtained as a function of, for example. 

stirrer bar M, magnetic stirrer F, filter H, shutter L, arc lamp  

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