TIME-DEPENDENT LIGHT-ABSORPTION BY IMPURITY CENTERS

Light absorption by impurity centres with generation of charge-transfe r excitons is considered. The static electric field produced by alread y existing excitons shifts the excitation energy of non-excited centre s and, hence, the probability of their excitation. This dependence of the absorption cross-section of a centre on the spatial distribution o f excitons results in the nonlinear behaviour of the system under stro ng pumping. Computer simulation of exciton generation and annihilation shows that stationary powerful light transmitted through a sample has a time dependent power.