Anomalous decay of the slow emission component in doped alkali halides

We provide a wide class of experimental fits in support of a model previous ly proposed to explain anomalous nonexponential decay of the slow luminesce nce component of Pb2+ centers in alkali halide crystals. The model was base d on the assumption that the lattice relaxes on the same time scale as the slow-component decay time. This relaxation is a response to the Jahn-Teller local distortion of the Pb2+ luminescence centers. The original work studi ed KBr:Pb2+ centers (at LHe temperature). We now apply the method to fit ex perimental data for the slow-component decay of KX:Pb2+ and KX:Tl+ (X=Cl, B r, I). An essential feature of the model is that lattice relaxation causes a time-dependent coupling of the Jahn-Teller levels. In the first place, th e present successful fits provide evidence for the mechanism earlier propos ed. Moreover, the dependence of the fitting parameters on lattice and impur ity features allow systematic physical interpretation. (C) 2001 Elsevier Sc ience B.V. All rights reserved.