Spectral Intensities Of F-f Transitions In Rare-earth Ions Doped Crystals

The main purpose of this thesis is to introduce the spectral intensities of f-f transitions in rare-earth ions doped crystals. In part one, the closure approximation in Judd-Ofelt breaks down when applied to the high-lying state of 4fN configuration. Modification has been done to the traditional theory. In part two, the luminescence properties of a long-lasting phosphor are studied. The emitting intensities from the low-lying state of 4fN configuration are obtained by Judd-Ofelt treatment. The main results obtained are listed as follows:1. A modified Judd-Ofelt theory is to treat the electric dipole transitions within the 4f2 configuration of Pr3+ doped CaAl12O19 and SrAl12O19 by considering two main perturbing components of 4f5d and 4fn'g. The explicit distance between the 4f5d configuration and the 4f2 energy levels are determined. The odd-λintensity parameters are included. The intensity parameters are obtained by fitting the experimental emitting intensities and lifetime of 3P0. Next, the emitting line intensities and lifetime originating from 3P0 and 1S0 are then calculated. Compared with the experimental measurements, the modified model yields better results than the standard Judd-Ofelt theory.2. The effects of 4f25d configuration on the intraconfigurational 4f3?4f3 electric dipole transitions of Nd3+ doped YPO4 are taken into account by a"direct"calculation. A simple model is applied to analyze the opposite parity 4f25d configuration. The matrix elements of the odd-rank crystal-field interaction and the interconfigurational electric dipole transition are directly expressed using a standard tensor operator method. A set of selection rules for f-d mixing and f-f electric dipole transitions is built up. Using this calculation method in combination with the experimental data from the absorption spectrum, a set of intensity parameters is obtained. The transition intensities originating from the high-lying 2G9/2(2) level to the lower energy levels are then calculated, demonstrating a good agreement with the experimental results.3. We report a persistent phosphor of KY3(1-x)Tb3xF10 (KY3F10:xTb3+) for X-ray or cathode ray tubes. The phosphorescence consists of a group of blue and green emission lines originating from 5D3→7FJ and 5D4→7FJ transitions of Tb3+, respectively. The phosphorescent emitting color can be tuned from blue to green by gradually increasing Tb3+ concentrations due to the cross-relaxation described by ( 5D3, 7F6 )– ( 5D4 , 7F0 ). The Tb3+ concentration dependent phosphorescence spectra are well simulated based on the analysis of luminescence dynamical processes using Judd-Ofelt theory and rate equations concerning the 5D3 and 5D4 levels.