稀土离子间反斯托克斯能量传递计算的改进 1.实验及理论基础

从理论和实验上研究了红绿荧光强度反转现象。实验测量发现Er(0.5)Yb(9.5)∶FOV纳米相氟氧化物玻璃陶瓷存在强的红绿荧光强度反转现象,实验测量得到其红绿荧光强度反转动态范围为877,同时计算了Er(0.5)Yb(9.5)∶FOV的所有基础光谱参量,建立了对系统所有稀土离子能级的动力学过程进行数值模拟计算的理论基础。     

稀土离子发光体系中能量传递和迁移模型的研究

基于以前综合V-F模型(考虑施主受主(D-A)能量传递)和B模型(考虑施主施主(D-D)能量迁移)而提出的V-F-B综合模型,对La_1-xEr_xF₃体系中Er³⁺离子四种低掺杂浓度下(x=0.001,0.003,0.01,0.02)295K时⁴S_3/2→⁴I_15/2发光的时间演化曲线成功地重新进行了数值拟合.结果表明该体系内D-A间交叉弛豫能量传递是偶极-偶极作用,作用常数C_DA为4.75×10^-41cm⁶/s,与Okamoto等人原用YT扩散模型得到的结果一致.而拟合得到的四个D-D平均跳跃时间τ₀粗略地与x_D^α次方(x_D为D离子浓度)成正比(α≈-1.237),并不遵从τ₀很小时与x_D的-2次方成正比的理论关系.同时,通过把D-D迁移和D-A传递同时同样地纳入V-F模型还粗略估计了D-D平均跳跃时间τ₀′的值,发现它与V-F-B给出的τ₀拟合值比较一致,说明V-F-B模型在一定近似程度上是内部自恰的、合理的. 关键词： 能量传递 能量迁移 跳跃时间 交叉弛豫     

稀土离子的多格位占据及能量传递

多格位占据及其能量传递普遍存在于稀土发光材料的各个领域,且具有重要的科学及现实意义。Ce³⁺的4f-5d和Eu³⁺的4f-4f跃迁代表了稀土离子两种典型的电子跃迁类型。我们以Ce³⁺或Eu³⁺分别激活的E(δ)-Gd₂Si₂O₇(Pnma)、G-La₂Si₂O₇(P2₁/n)和F-Eu₂Si₂O₇(■)为代表案例,讨论和思考稀土离子的多格位占据及其非辐射能量传递,重点阐述了晶体结构、样品相纯度、掺杂浓度、光谱测试、格位间能量传递和光谱分辨率等需关注的事项。在稀土离子激活的发光材料研究中,我们既需考量材料晶体结构与光谱的自洽,也要从光谱及发光衰减动力学对格位间能量传递(包括传出能量和接收能量)方面进行分析。希望这些内容在实验及表征上对刚涉足相关领域的读者有所启发。     

镧系离子间无辐射能量传递速率的教程综述（英文）

在本教程综述中,我们重新阐述和表达了镧系离子间无辐射能量传递(ET)速率的理论形式,并且强调了考虑镧系离子本身特异性所引发的与F?rster和Dexter理论不同之处。所给出的表达式遵循了Judd-Ofelt的4f-4f跃迁理论框架之下的Kushida方法,并计入了如下电多极机制：偶极-偶极(W_d-d)、偶极-四极(W_d-q)和四极-四极(W_q-q)。更为重要的是,当前的机制也扩展包括了交换(Wex)和磁偶极子-磁偶极子(W_md-md)作用,并经过改进进一步包含了屏蔽效应以及给出了F因子(费米黄金规则中的态密度)的解析表达式。与Kushida的原始方法类似,我们只考虑了强制电偶极子(FED)对Judd-Ofelt强度参数的贡献,并细节性地讨论了磁偶极-磁偶极相互作用的选择定则以及相关矩阵元的计算。此外,我们还以Tb(Ⅲ)-Eu(Ⅲ)和Yb(Ⅲ)-Er(Ⅲ)的能量传递速率计算为例,逐步展示了计算过程、主要的计算支撑信息以及所使用的计算脚本。     

Tb3+掺杂Y2O3纳米晶体中Tb3+离子4f5d跃迁及能量传递的研究

采用燃烧法制备了不同Tb3 掺杂浓度和不同粒径的Y2O3:Tb纳米晶体粉末样品,并通过高温退火获得了相应Tb3 掺杂浓度的体材料样品。测量了纳米和体材料样品的发射光谱、激发光谱、X射线衍射谱和荧光衰减曲线,并拍摄了不同粒径样品的透射电子显微镜(TEM)照片。研究纳米Y2O3∶Tb晶体粉末中Tb3 离子的4f5d跃迁发现,由于在近表面的低结晶度环境和颗粒内部的高结晶度环境中Tb3 离子4f5d跃迁对应的激发峰位置不同,不同粒径样品中处于这两种环境的Tb3 离子比例也不同,激发谱的谱线形状存在较大差别,还对Tb3 离子的能量传递进行了研究,发现Y2O3∶Tb晶体粉末中Tb3 的(5D3,7F6)→(5D4,7F0)能量传递类型为受纳米限域效应影响很大的电偶极电偶极相互作用;引起5D4→7F5(543nm)发光浓度猝灭的是不同Tb3 离子5D4能级之间交换相互类型的能量传递,此类型的能量传递受纳米限域效应影响较小。     

外周天线色素分子间的能量传递

依据外周天线LHCII的吸收光谱和解叠谱,将LHCII中大量的色素分子分为4类色素分子团,建立了色素分子团的能量传递模型,并分别在436nm、480nm激励光下,对它的荧光光谱进行了研究,436nm和480nm激励下的荧光光谱相比要弱,可能是由于436nm激励下,受激的一部分色素分子的振动自由度比较大,产生了激发态到基态的无辐射内转换,使得能量传递几率降低.同时也说明,不同色素分子间的能量传递几率是不同的.     

多声子参与的三价稀土离子反斯托克斯荧光

迄今为止,与三价稀土离子荧光有关的多声子协助现象的研究工作主要考虑了无辐射衰减和能量传递(1,2,3)。而对于这种弱偶合限制中的多声子参与的反斯托克斯和斯托克斯边带激发仅做了少量实验工作,主要因为通常限于一个声子边带(4)。此外,Miyakwa和Dexter指出,多声子边带是稀土离子间多声子协助能量传递中出现的重叠积分理论计算中的一个中间步骤(5)。     

1-乙酰乙酰基-3-甲基吲哚对稀土离子能量传递过程研究

通过1-乙酰乙酰基-3-甲基吲哚(I3MK)与各种稀土离子在77K乙醇刚性溶液体系中的荧光光谱、磷光光谱的测定,进行了I3MK向稀土离子能量传递过程的静态分析;从I3MK和I3MK-Tb(Ⅲ)体系的荧光寿命、磷光寿命、量子产率,时间分辨光谱等,计算了各主要能量传递过程的速率常数和能量传递效率,进行了该体系能量传递过程的动态分析,提出了Perrin公式的修正参数,讨论了I3MK-Tb(Ⅲ)体系的能量传递机理.     

Gd2O3:(Ce3+,Eu3+)微晶中稀土离子间的级联能量传递

本文了纳米Gd2O3:(Ce^3 ,Eu^3 )的紫外与真空紫外（UV-VUV)激光谱及其选择激发下的荧光光谱,这些光谱实验表明,除Gd2O3基质与Ce^3 ,Eu^3 离子之间的能量传递外,还存在着Gd^3 与Ce^3 ,Eu^3 间的能量传递,即存在Gd^3 →Ce^3 →Eu^3 三种稀土离子间的级联传递。     

Gd_2O_3∶(Ce~(3+),Eu~(3+))微晶中稀土离子间的级联能量传递

本文报道了纳米Gd2 O3∶(Ce3+ ,Eu3 + )的紫外与真空紫外 (UV VUV)激发谱及其选择激发下的荧光光谱。这些光谱实验表明 ,除了Gd2 O3 基质与Ce3+ ,Eu3 + 离子之间的能量传递外 ,还存在着Gd3+ 与Ce3 + 、Eu3 +间的能量传递 ,即存在Gd3+ →Ce3+ →Eu3 + 三种稀土离子间的级联传递     

Photoluminescence and energy transfer processes in rare earth ion doped oxide thin films with substrate heating

Tm-Er codoped amorphous aluminum oxide thin films were prepared by pulsed laser deposition. Broadband photoluminescence in the wavelength region of 1400-1700 nm comprised of two emissions at around 1532 and 1620 nm was observed. PL performance was investigated as a function of the substrate-heating temperature. Possible energy transfer processes involved in the heat treatment were discussed and nonradiative decay rates were evaluated, by comparing the inverse of measured lifetimes with the calculated radiative decay rates. Our results suggest that Tm-Er codoped Al₂O₃ thin film might be potential candidate as broadband light sources and amplifiers.     

Ba-Sr系统激光感生碰撞能量转移的数值计算

以现有的激光感生碰撞能量转移的四能级理论模型为基础,通过直接积分态振幅的运动方程,对弱场、强场两种情况下Ba-Sr系统的激光感生碰撞能量转移过程进行了数值计算,得到了两种情况下的激光感生碰撞跃迁概率和碰撞截面的谱线线型.在弱场情况下的数值计算结果与近似解析解的计算结果符合很好.对强场情况下的数值积分计算结果表明：激光感生碰撞作用随转换激光强度的增大而增强;强场时激光感生碰撞截面谱线的峰值位置明显偏离了共振频率并向紫端移动,且碰撞截面谱线的半宽度(即调谐范围)较之弱场明显变小. 关键词： 激光感生碰撞能量转移 碰撞截面 Ba-Sr系统 强场     

高激发振动态RbH（Х1Σ+,ν″=15～22）与H2,N2的振动-振动碰撞能量转移

脉冲激光激发Rb原子至6 D态,Rb(6 D)与H2反应生成RbH(Х1Σ+,ν″=0～2)振动态。研究了RbH(Х1Σ+)高位振动态与H2,N2间的碰撞弛豫过程,利用泛频泵浦分别激发Х1Σ+(ν″=0)至Х1Σ+(ν″=15～22)各振动态,检测激光激发Х1Σ+(ν″)至A1Σ+(ν′),测量A1Σ+(ν′)的时间分辨激光感应荧光光谱,利用Stern-Volmer方程,得到振动能级ν″的总的弛豫速率系数kν(H2)。在H2和N2的混合气体中,总弛豫速率系数kν(H2+N2)与α(H2的摩尔配比)成直线的关系,其斜率为kν(H2)-kν(N2),而截距为kν(N2)。对于ν″<18主要发生单量子弛豫(Δν=1)过程,kν(H2)和kν(N2)与振动量子数ν″均成线性增加关系。对于ν″≥18,多量子弛豫(Δν≥2)过程及共振振动-振动转移起重要作用。对于RbH(ν″=21)+N2(0),测量ν″=16的布居数时间演化轮廓,在20μs内有一个锐锋,在100～200μs内有一个较低的宽峰,锐锋相应于RbH(ν″=21)+N2(0)→RbH(ν″=16)+N2(1)的共振转移过程,而宽峰是由相继的单量子过程产生的。     

Mechanisms of fluorescence enhancement in rare earth sol-gel glass containing Al

Analysis of glasses containing Eu and Tb dopants yields new insights about the role of Al³⁺ co-doping in improving fluorescence yield of glasses containing rare earth (RE) dopants. Our work suggests that Al co-doping enhances fluorescence by two important mechanisms. (1) At low Al:RE ratio the site symmetry is lowered, allowing more admixture of opposite parity wavefunctions and increased transition probability. (2) At high Al:RE ratio, the highest frequency phonons are of lower energy; so nonradiative decay rates are reduced. In addition, a new technique - post-annealing immersion - is introduced, which allows the study of RE location in the sol-gel matrix. Al co-doping is observed to increase the tendency for RE ions to reside on pore surfaces.     

Inverse bottleneck in Eu-Mn energy transfer

The energy transfer (ET) between Eu²⁺ and Mn²⁺ in Ca₅(PO₄)₃Cl has been investigated. At low intensities under 405 nm excitation, time-resolved experiments provide microscopic parameters for the energy transfer between adjacent Eu²⁺ and Mn²⁺ ions. At high intensities, we observe a non-linear component in the energy transfer process due to ground state depletion of the Mn²⁺ ions, leading not to a reduction, but to an increase in the energy transfer rate between Eu²⁺ and Mn²⁺ ions and also energy transfer between excited Mn²⁺ ions. This results in a sub-linear response of both Eu²⁺ and Mn²⁺ luminescence as a function of intensity. Our observations are quantitatively described by a model using energy transfer to Mn²⁺ ions in both the ground and the excited state.     

Electronic energy transfer in benzophenone adlayer

The extent to which energy transfer occurs in electronically excited organic adlayer films on dielectric surfaces is investigated. Migration and subsequent trapping of the energy in the film are observed by pumping the singlet state of an organic adlayer of benzophenone and by monitoring the phosphorescence and fluorescence lifetimes. To observe the effects of adsorption, benzophenone was chosen as the adlayer because the energies of its well characterizedn, carbonyl states are remarkably sensitive to solvent interactions. Upon excitation with a nitrogen laser, the perturbation on the electronic states of benzophenone by the substrate caused the emergence of the normally absent fluorescence from the adlayer traps at the interface between the surface of the dielectric substrate and the adlayer. Energy transfer to this interface was observed as a function of film thickness. On the surface of a single crystal of an organic crystal, naphthalene, energy transfer from the adlayer to the substrate was observed, whereas such transfer was not energetically possible with the other dielectric surfaces.     

Influence of donor-donor transport on excitation energy transfer

Energy migration and transfer from acriflavine to rhodamine B and malachite green in poly (methylmethacrylate) have been investigated using the decay function analysis. It is found that the influence of energy migration in energy transfer can be described quite convincingly by making use of the theories of Loring, Andersen and Fayer (LAF) and Huber. At high acceptor concentration direct donor-acceptor transfer occurs through Förster mechanism.     

Study on the chemiluminescence resonance energy transfer between luminol and fluorescent dyes using a linear CCD spectrometer

Chemiluminescence (CL) has been a useful tool for analytical applications. Fluorescein can be used to enhance CL emission of luminol. With three-dimensional (3D) dynamic CL spectrum obtained from a linear CCD (charge-coupled device) flow-injection CL spectrometer, the fluorescein enhanced CL analysis was studied. The enhanced process can be described with chemiluminescence resonance energy transfer (CRET) at certain fluorescein concentrations. In the process of CRET, fluorescein enlarges CL intensity but does not join the CL reaction. Compared with classic luminol-Co²⁺ CL system, the fluorescein-enhanced system exhibits stronger CL signal with the linear range and detection limit for traces of Co²⁺ unchanged.