Apparent differential quantum yield

3 Apparent differential quantum yield The apparent differential quantum yield 

All the quantum yields defined so far cannot give a correct view of the photokinetics. pc as well as Yc and Yc depend in a very complex manner on the time of irradiation. Therefore in Section 2.1.2, two other yields are defined which take into account that the amount of light absorbed during the photoreaction changes and the photochemical process can combine more than one step of photochemistry. 

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One of the most important features of a photoreaction is the value of the quantum yield ( )i of compound i, which is the quantifying answer to the question How effective In principle, the quantum yield is the ratio of the number of reacting molecules to the number of quanta absorbed. In praxis there are several definitions of the quantum yield true (only light absorbed by the reactant is considered) and apparent (there are other absorbers present), differential (at the moment ) and integral (mean). In the previous rate equation, ( )e and (j) are the true differential yields. The monoexponential kinetics of Equation, 1.2 or 1.4 allow one to determine the yields in systems where the starting solution is already a mixture of E- and Z-forms (which can happen easily if the E-form is not prepared under strict exclusion of light). It turns out, however, that the yalues of the Z —> E quantum yield are especially sensitive to small errors in the E values. 

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