4fn→4fn-1 5d transitions of the heavy lanthanides: Experiment and theory
4fn→4fn-1 5d transitions of the heavy lanthanides: Experiment and theory
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DOI：
10.1103/physrevb.65.045114
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发表时间：
2002-01
影响因子：
3.7
通讯作者：
L. V. Pieterson;M. F. Reid;G. Burdick;A. Meijerink
中科院分区：
文献类型：
--
作者：
L. V. Pieterson;M. F. Reid;G. Burdick;A. Meijerink
在紫外和真空紫外光谱区（100-275 nm）研究了LiYF 4 、CaF 2 和YPO 4 中掺入的重镧系元素（Tb 3 + 、Dy 3 + 、Ho 3 + 、Er 3 + 、Tm 3 + 和Yb 3 + ）的 4f n →4f n 1 5d(fd) 激发光谱。所有重镧系元素都观察到自旋禁止跃迁和自旋允许跃迁。在激发光谱中，可以清楚地观察到 5d 电子的晶体场分裂。对于高自旋和低自旋 fd 能带，观察到向最低 5d 晶体场分量的过渡的精细结构（零声子线和振动线）。能级和强度计算是通过 4f n 态能级计算常用模型的扩展来执行的。使用描述 Sd 晶体场分裂的参数（来自 Ce 3 + 的光谱）、4f n 核分裂的参数（来自 4f n 态能级计算的文献）以及 5d 电子的自旋轨道耦合和 4f 和 5d 电子之间的库仑相互作用的参数（来自原子从头计算），实验和模拟光谱之间获得了良好的一致性 使用 Cowan 的计算机代码）。为了提高模型和实验之间的一致性，稍微调整了 5d 晶体场参数，以纠正由于镧系元素收缩而导致的较重稀土的晶体场强度下降。氟化物主晶格中的 f-d 相互作用参数减少至计算的自由离子值的约 67%，以补偿云斜效应。
The 4f n →4f n 1 5d(fd) excitation spectra of the heavy lanthanides (Tb 3 + , Dy 3 + , Ho 3 + , Er 3 + , Tm 3 + , and Yb 3 + ) incorporated in LiYF 4 , CaF 2 , and YPO 4 are investigated in the ultraviolet and vacuum-ultraviolet spectral region (100-275 nm). Spin-forbidden transitions as well as spin-allowed transitions are observed for all heavy lanthanides. In the excitation spectra the crystal-field splitting of the 5d electron can be clearly observed. Fine structure (zero-phonon lines and vibronic lines) is observed for the transition to the lowest 5d crystal-field component, for both the high-spin and low-spin fd bands. Energy-level and intensity calculations are performed by an extension of the commonly used model for energy-level calculations of 4f n states. A good agreement between experimental and simulated spectra is obtained, using parameters that describe the Sd crystal-field splitting (from the spectra of Ce 3 + ), the parameters for the splitting of the 4f n core (from the literature on energy-level calculations for 4f n states) and parameters for the spin-orbit coupling of the 5d electron and the Coulomb interaction between 4f and 5d electrons (from atomic ab initio calculations using the computer code of Cowan). To improve the agreement between the model and experiment the 5d crystal-field parameters were adjusted slightly to correct for the decreasing crystal-field strength for the heavier rare earths due to the lanthanide contraction. The f-d interaction parameters in the fluoride host lattices were reduced to about 67% of the calculated free-ion values in order to compensate for the nephelauxetic effect.