【作者】 张金苏；

【导师】 张家骅； 王笑军；

【作者基本信息】 中国科学院研究生院（长春光学精密机械与物理研究所） ， 凝聚态物理， 2010， 博士

【摘要】 本论文主要介绍晶体中稀土离子f-f跃迁光谱强度的理论研究工作。具体工作分为两部分:第一部分,解决由于Judd-Ofelt理论中的“締合近似”,计算稀土离子4fN组态高能级的发射光谱强度存在很大偏差,修正了传统的理论。第二部分中,对一种X射线或阴极射线激发长余辉材料的光谱性质进行研究,应用Judd-Ofelt理论计算了其掺杂稀土离子4fN组态低能级的发射光谱强度,进而实现了对实验现象的解释。主要内容及结果如下:1对Pr3+掺杂的CaAl12O19及SrAl12O19体系进行研究,给出了Pr3+的4f2组态内电偶极跃迁强度的计算方法。考虑到由于4f2组态各能级与4f5d混杂态的能量差不同,对传统全参量Judd-Ofelt理论进行修正,计算中引入了λ为奇数的强度参数。根据实验测量的3P0能级向下能级发射强度比以及它的寿命值就可以得到这些强度参数值。将得到的强度参数值回代到跃迁几率的计算中,得到3P0能级及1S0能级寿命及向下各个能级的跃迁强度,计算结果表明修正的Judd-Ofelt理论处理高能级的发射强度有很大的改进。2选取了YPO4:Nd3+体系,考虑了4f 25d组态对f-f跃迁的明确影响。用Duan的简单模型处理4f 25d组态。应用标准张量方法对奇次晶场作用和组态间的电偶极跃迁矩阵元直接展开得到f-f电偶极跃迁强度表达式,其中包含了决定f-d混杂定则的数学因子和需由实验数据拟合的强度参数。由基态4I9/2的吸收强度来拟合这些强度参数,并回代到振子强度的计算中,得到了基态吸收的振子强度及高能级2G(2)9/2向下能级发射的强度,结果表明此模型的建立是合理的。3研究Tb3+掺杂的KY3F10体系在X射线或阴极射线激发下的余辉现象。由于( 5D3, 7F6 )– ( 5D4 , 7F0 )的交叉弛豫,余辉颜色随Tb3+掺杂量的不同而可调。由Judd-Ofelt理论计算得到了5D3、5D4能级的光谱学参量,结合发光动力学的分析,给出了交叉弛豫的速率、效率及蓝绿余辉强度比,理论计算结果和实验结果相一致。更多还原

【Abstract】 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.更多还原