Anomalous decay of the slow emission component in doped alkali halides

We provide a wide class of experimental fits in support of a model previously proposed to explain anomalous non-exponential decay of the slow luminescence component of Pb2+ centers in alkali halide crystals. The model was based 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 studied KBr : Pb2+ centers (at LHe temperature). We now apply the method to fit experimental data for the slow-component decay of KX : Pb2+ and KX : Tl+ (XCl, Br, 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, the present successful fits provide evidence for the mechanism earlier proposed. Moreover, the dependence of the fitting parameters on lattice and impurity features allow systematic physical interpretation.