CaS:Pr,Na的激光选择激发

本文用激光选择激发研究了CaS:Pr,Na中Pr³⁺的³P₀→³F₂发光,分辨出5种不同的Pr中心。用三个参数描述立方晶场中受电荷补偿结构影响的稀土离子的能级劈裂,其中两个参数是立方晶场参数B₄和B₆,另一个反映引入电荷补偿结构后立方晶场的畸变。对³F₂能级劈裂的拟合结果表明,发光来自受不同距离上电荷补偿结构影响的Pr中心.     

Li+离子掺杂Gd2O3：Sm3+纳米晶的发光增强

采用燃烧法制备了Gd₂O₃:Sm³⁺和Li⁺离子掺杂的Gd₂O₃:Sm³⁺纳米晶,根据X射线衍射图谱确定所得纳米样品为纯立方相。在室温下,用275 nm和980 nm激发光激发各样品时,可分别观测到Sm³⁺离子的强荧光发射和上转换特征发射,其主发射峰分别位于560,602,650 nm处,分别对应着Sm³⁺离子的⁴G_5/2→⁶H_5/2,⁴G_5/2→⁶H_7/2和⁴G_5/2→⁶H_9/2的电子跃迁,其中以⁴G_5/2→⁶H_7/2跃迁的光谱强度最大。实验表明Li⁺离子的掺入使得Sm³⁺离子的荧光发射强度显著增加。通过对样品的XRD、TEM和激发光谱、发射光谱的研究,分析了引起样品荧光强度变化的原因。     

Na+离子掺杂Gd2O3 ∶ Sm3+纳米晶的发光增强

采用柠檬酸作燃烧剂,在柠檬酸-硝酸盐体系下制备了Gd₂O₃ ∶ Sm³⁺和Gd₂O₃ ∶ Sm³⁺,Na⁺纳米晶。用X射线衍射仪、透射电子显微镜、荧光光谱仪等对样品的结构、形貌和光致发光性能进行了分析。结果表明:所得纳米样品为纯立方相,晶粒尺寸约为30 nm。在室温下,用275 nm激发光激发各样品时,可观测到Sm³⁺离子 的较强发光,其主发射峰位分别位于561.5,603.5,651.5 nm,分别对应着Sm³⁺离子的⁴G_5/2→⁶H_5/2 , ⁴G_5/2→ ⁶H_7/2 和⁴G_5/2 →⁶H_9/2的电子跃迁, 其中以⁴G_5/2→⁶H_7/2 跃迁的光谱强度最强。实验表明:Na⁺离子的掺入使得Sm³⁺离子的光发射强度显著增强。对引起样品荧光强度变化的原因进行了分析。     

四角对称晶场中4B1(3d3)态离子的磁相互作用及其自旋哈密顿参量研究

基于完全对角化方法，研究了⁴B₁(3d³)态 离子在四角对称晶场中的磁相互作用，分析了自旋哈密顿参量(b⁰₂, g_∥, g_⊥ , Δg)的微观起源.结果表明 ：在被考虑的大部分晶场区域，人们通常考虑的SO(spin-orbit)磁相互作用的贡献最为重要 ；然而，对于零场分裂参量b⁰₂而言，来自其他机理(包 括SS(spin-orbit)，SOO(sp in-other-orbit)，SO-SS-SOO)的贡献在大部分晶场区域超过了20％；在部分晶场区域，其 他机理的贡献甚至超过SO机理的贡献.详细地分析了Macfarlane 零场分裂参量b^{0₂ 近似三阶微扰理论的收敛性，结果表明：该理论在大部分晶场区域收敛性较差.讨论了3d3}态离子第一激发态²E_g分裂的微观起源.并利用 群论方法解 释了在C_4v和C_3v对称晶场中²E_{g< /sub>态分裂的不同机理. 关键词： 4B1(3d³)态离子')" href="#">⁴B1(3d³)态离子 磁相互作用 自旋哈密 顿参量 完全对角化方法(CDM) 微扰理论方法(PTM)}     

α-Fe2O3单离子磁晶各向异性的计算及Morin转变的解释

本文根据晶场理论计算了α-Fe₂O₃的单离子磁晶各向异性。采用点电荷模型,计及近邻及次近邻对晶场的贡献,并考虑到近邻O^2-离子对次近邻Fe³⁺离子的电屏蔽效应,在六级微扰近似下,得到单离子各向异性场H_si=102.3×10²Oe。这一结果结合Artman等人对磁偶极各向异性的计算,导出了α-Fe₂O₃的Morin转变温度T _关键词：     

四角或三角畸变立方晶场中(3d)1过渡金属离子的劈裂因子

对四角或三角畸变立方晶场中的(3d)¹离子,在已有的静电晶场理论的基础上,采用“集团模型”,进一步引入Γ_∥, Γ_⊥及K_∥, K_⊥,R_∥, R_⊥,并考虑E_g混入T_2g,导出适用于四角或三角畸变立方晶场各种可能情况的g_∥, g_⊥公式。讨论了g_∥, g 关键词：     

BeAl2O4:Cr3+的晶场能级

金绿宝石中镜对称格位上Cr³⁺(Ⅱ)离子的⁴T₂,⁴T₁和²E能级与该材料的激光运转有关。⁴T₂和⁴T₁能级各分裂成三个子能级。为从偏振吸收谱上确定BeAl₂O₄:Cr³⁺的能级图,本文计算了⁴T₂和⁴T₁的分裂,找到了对谱方法,得到了表征能级分裂的参量K_{1和K2的值。最后给出了以低点群不可约表示标号的、BeAl2O4:Cr³⁺(Ⅱ)的晶场能级图。 关键词：}     

ZBLAN玻璃中Pr3+掺杂离子3P0和1D2能级的发光特性和寿命

对ZBLAN氟锆酸盐玻璃中Pr³⁺掺杂离子³P₀和¹D₂能级的寿命和发光特性进行了较详细的光谱学研究。首先测量了两种掺杂浓度(质量分数分别为1×10^-3,5×10^-3)的Pr³⁺:ZBLAN玻璃的吸收光谱,然后运用时间分辨激光光谱技术测量了³P₀和¹D₂能级在激光单光子共振激发下的荧光发射谱和能级寿命。将不同荧光发射谱带的强度和文献报道的Judd Ofelt理论计算辐射跃迁几率数值做了比较分析,证明了文献中理论计算结果的可靠性。由于浓度猝灭效应,在相同的激发条件下,掺杂浓度为1×10^-3样品的荧光发射强度明显大于5×10^-3样品的荧光发射强度。但是从我们的测量结果看,掺杂浓度对³P₀和¹D₂ 的能级寿命值无显著影响。掺杂浓度为1×10^-3时,Pr³⁺离子³P₀和¹D₂能级的寿命值分别为46,322μ_s。     

2018年9期电子期刊

采用高温固相法在1 150℃下经二次煅烧合成了双钙钛矿型的红色荧光粉Sr₂ZnTeO₆∶xEu³⁺（x=0.05-0.40）,并进行了相组成、发光性质和热稳定性的研究。结果表明,所合成的Sr₂ZnTeO₆与Sr₂ZnWO₆具有相同的结构,掺杂离子的加入没有改变相结构。样品的激发光谱由电荷迁移带和Eu³⁺离子的特征激发峰组成,主激发峰位于464 nm（⁷F₀→⁵L₆）。样品的发射光谱位于614 nm（⁵D₀→⁷F₂）。Sr₂ZnTeO₆∶xEu³⁺荧光粉的发光强度随着Eu³⁺离子的掺杂,先增大后减小,在x≥0.25时,发生浓度猝灭现象。通过变温荧光发现它具有非常好的热稳定性。由于荧光粉的最佳激发位于464 nm,因而可以用于蓝光激发下的白光LED的红色荧光粉。     

GdOBr∶Eu晶场参数与自由离子参数的高压研究

在GdoBr∶Eu的常压和高压荧光谱实验数据基础上，对晶场能级及其重心进行了拟合计算，得到了晶场参数和自由离子参数（Slater参数和自旋 轨道耦合参数）在高压下的变化情况．计算结果表明，随压力增大，晶场参数B⁴₀，B⁶₀增大，B⁶₄减小，B²₀，B⁴₄的变化有些起伏．晶场强度在8GPa以 关键词：     

Pr3+在SBN晶体中的发光特性

通过测量Ｐｒ：ＳＢＮ晶体的吸收光谱和荧光光谱来确定Ｐｒ³⁺在ＳＢＮ晶体中的能级位置。由于Ｐｒ³⁺离子占据晶体中的不同格位而引起荧光带呈现双峰结构。测量荧光寿命随温度的变化关系，表明Ｐｒ³⁺在ＳＢＮ晶体中 ³Ｐ₀态的无辐射弛豫主要是 ³Ｐ₀→¹Ｄ₂多声子弛豫过程。 关键词：     

Time-resolved site-selection spectroscopy studies of NdAl3(BO3)4 crystals

A pulsed, tunable dye laser was used to selectively excite Nd³⁺ ions in nonequivalent crystal field sites in NdAl₃(BO₃)₄ crystals and energy transfer between ions in different types of sites was studied by monitoring the time evolution of the fluorescence spectrum. The results show that the energy transfer rate varies as t^{$\text{-1}\text{2}$} and increases with temperature. The predictions of various models of phonon-assisted energy transfer are compared to the results.     

Crystal-field analysis of Tb3+ doped yttrium aluminium garnet using site-selective polarized spectroscopy

The optical isotropy of the cubic garnet was overcome by crystal-site selective excitation and fluorescence spectroscopy. Thus the symmetries of the crystal-field states of the free ion levels⁷F _J and⁵D₄ could be determined. On this basis a crystal field analysis was performed to derive the crystal-field parameters for the Tb³⁺ ions replacing the Y³⁺ ions on the D₂ sites.     

Spectral properties of Pr3+ ions in Bi2(MoO4)3 crystal

A Bi₂(MoO₄)₃ single crystal doped with Pr³⁺ ions has been grown by the Czochralski technique. The polarized absorption and fluorescence spectra as well as the fluorescence decay curve of Pr³⁺ ions in the crystal were measured at room temperature. The spectroscopic parameters, including the Judd–Ofelt intensity parameters Ω_t (t=2, 4, and 6), spontaneous emission probabilities, fluorescence branching ratios, radiative lifetimes, stimulated emission cross sections, and fluorescence quantum efficiencies, were calculated. The spectral properties related to laser performance of this crystal were analyzed. The ¹ D ₂ multiplet of the crystal may be a good upper level for a solid-state laser.     

Laser time-resolved selective excitation of Nd3+ ions in KNdP4O12 crystals

The emission spectra of Nd³⁺ ions in KNd_xRE_1?xP₄O₁₂ (RE = Y, La and Pr) and KNd_xCr_1?xP₄O₁₂ crystals were investigated. Under selective excitation into ²G$\text{7}\text{2}$ + ⁴G$\text{5}\text{2}$ multiples at 1.6 K the fluorescence of Nd³⁺ ions in non-equivalent crystal sites was observed. The excitation spectrum of the ${}^4\text{F}\text{3}\text{2}$ fluorescence had a complex satellite structure. Time resolved measurements showed the dependence of the fluorescence decay on the excitation wavelength. Selective excitation into the satellite lines at the wings of the main transition led to strongly non-exponential decay. The low temperature results indicated that there is no spectral energy transfer between ions in different types of sites.     

Polarized spectroscopic properties of Nd-doped KGd(WO4)2 single crystal

The polarized absorption spectra, infrared fluorescence spectra, upconversion visible fluorescence spectra, and fluorescence decay curve of orientated Nd³⁺:KGd(WO₄)₂ crystal were measured at room-temperature. Some important spectroscopic parameters were investigated in detail in the framework of the Judd-Ofelt theory and the Fuchtbauer-Ladenburg formula. The effect of the crystal structure on the spectroscopic properties of the Nd³⁺ ions was analyzed. The relation among the spectroscopic parameters and the laser performances of the Nd³⁺:KGd(WO₄)₂ crystal was discussed.     

Fluorescence properties of divalent and trivalent europium ions in CdWO4 single crystals grown by Bridgman method

Optical absorption, excitation, and fluorescence were investigated in Eu ion-doped CdWO₄ single crystal grown by a modified Bridgman method. The results indicate that Eu²⁺ and Eu³⁺ ions coexist in CdWO₄ crystal and an energy transfer occurs between these Eu²⁺ and Eu³⁺ ions. When the crystal is excited by 266-nm light, the energy corresponding to the 4f⁶5d to ⁸S_7/2 transition of Eu²⁺ ions results in the excitation of the Eu³⁺ ions to the ⁵D_J level. The effect on fluorescence of annealing in oxygen at various temperatures was investigated. The excitation intensity of Eu²⁺ ions at 266 nm decreases as annealing temperature increases from 300 K to 1073 K, but it remains at a certain equilibrium level when the annealing temperature is further increased.     

Laser excitation of single ion and clustered ion sites in SrF2 : Er3+

Selective laser excitation has been used to study the optical properties of the charge compensated sites in 0.0001%, 0.01%, 0.05% and 0.2% concentrations of SrF₂ : Er³⁺. Using a pulsed, tunable, narrowband dye laser, nine crystallographically inequavalent sites were observed, and the fluorescence and excitation lines associated with each were identified. Concentration dependences, ion pair energy transfer, and crystal field splittings were used to classify these sites as arising from either a single charge compensated Er³⁺ ion or clustered pairs of Er³⁺ ions. At lower concentrations, the four single ion sites dominated the spectra while at higher concentrations the cluster sites weredominant. Several of these sites were found to be similar to sites previously observed in CaF₂ : Er³⁺, and several were correlated to spectra of SrF₂ : Er³⁺ published by other workers.     

Polarized spectral analysis of Er3+ ions in biaxial Bi2(MoO4)3 crystal

An Er³⁺:Bi₂(MoO₄)₃ single crystal has been grown by the Czochralski technique. The Stark sublevels of the ⁴I_15/2 and ⁴I_13/2 multiplets of Er³⁺ ions in the crystal were determined. The polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay curve of the crystal were measured at room temperature and the relevant spectroscopic parameters, including the Judd–Ofelt intensity parameters, spontaneous emission probability, fluorescence branching ratio, radiative lifetime, and stimulated emission cross section, were estimated. The effect of re-absorption on the spectroscopic parameters was discussed. When the crystal was excited at 977 nm, up-conversion green fluorescence was observed and discussed.     

Growth, polarized spectral properties, and 1.5–1.6 μm laser operation of Er:Yb:Sr3Gd2(BO3)4 crystal

An Er:Yb:Sr₃Gd₂(BO₃)₄ crystal was grown by the Czochralski method. The polarized spectral properties of the crystal were investigated, including the polarized absorption and fluorescence spectra and fluorescence decay. The fluorescence quantum efficiency of the upper laser level ⁴I_13/2 of Er³⁺ ions and the efficiency of the energy transfer from Yb³⁺ to Er³⁺ ions were calculated. End-pumped by a diode laser at 970 nm in a hemispherical cavity, a 1.6 W quasi-cw laser at 1.5–1.6 μm with a slope efficiency of 18% and an absorbed pump threshold of 5.9 W was achieved in a 1.8-mm-thick Z-cut Er:Yb:Sr₃Gd₂(BO₃)₄ crystal. This crystal has a flat and broad gain curve at 1.5–1.6 μm and so is also a potential gain medium for tunable and short pulse lasers.