The Kinetics of Donor–Acceptor Transitions in ZnS Type Phosphors

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Abstract
The kinetics of luminescence of ZnS type phosphors is treated in the view of the donor‐acceptor model. The probabilities for different kinds of inter‐impurity transitions at zero temperature are compared. The kinetics for the decay of luminescence after flash excitation [1] is extended to the case of luminescence during and after excitation by a constant light source. The decay law in this case is completely different from the former one and agrees well with experimental results. The degree of excitation is given as function of acceptor and donor concentration and depth, and the dependence of light storage on these parameters is discussed. The kinetics developed here is shown to apply also to the thermally activated luminescence at finite temperature. In this way it is easily understood that decay curves at T = 0 and at finite temperatures may be very similar in spite of different mechanisms for the luminescent transitions.