掺Er3+玻璃上转换发光特性研究

采用高温熔制工艺制备了掺Er3+硅酸盐玻璃，应用Judd-Ofelt 理论计算了Er3+光谱参数， 发现玻璃中含有0.15 mol%Er2O3 时各参数取得最大值；分析了玻璃的吸收光谱随Er3+离子浓度的变 化关系；上转换光谱分析表明在522 nm、544 nm、658 nm 处有较强的绿光和红光，分别对应于 2H11/2→4I15/2、4 S3/2→4I15/2、4 F9/2→4I15/2 的跃迁，且522 nm 绿光强度和658nm 红光强度要远大于544 nm 绿光强度. 分析了上转换发光强度随泵浦功率和Er3+离子浓度的变化关系，揭示了上转换发光机制 主要是激发态吸收和能量转换，且均为双光子吸收过程.

铒镱共掺铅硅酸盐玻璃的光谱分析

采用传统的高温熔融工艺制备了铒镱共掺铅硅酸盐玻璃. 测量了样品的吸收光谱、荧光光谱和折射率， 利用McCumber 理论和Judd-Ofelt 理论计算了该玻璃系统中Er3+离子4I13/2→4I15/2 能级跃迁受激发射截面和荧 光寿命.该玻璃在1 536 nm 处受激发射截面σemi 为8.62×10-21 cm2；荧光寿命长达11.32 ms（实验测量值为9.26 ms）；在1536 nm 附近有很强的荧光发射，荧光有效线宽为46.5 nm；样品存在中心波长为580 nm 的4S3/2→4I15/2 跃迁的上转换荧光. 结果表明，该样品荧光寿命长，受激发射截面大，同时具有较弱的上转换发光等特性， 是制作高能脉冲光纤激光器的理想材料

稀土(Er, Nd, Yb, Pr, Ho, Sm)有机/无机杂化材料的制备及发光性能研究

目前，国内外对于铕和铽等稀土配合物的可见区发光和应用都有大量研究，但对具有近红外发光（800-1700 nm）性能的稀土配合物的研究还处于起步阶段。由于稀土的近红外发光在光纤通讯、激光系统及诊断学等方面应用具有特殊的优点，越来越引起人们的兴趣和重视。 稀土近红外发光配合物的致命弱点是其光、热和化学稳定性较差，从而限制了其在很多领域的实际应用。而溶胶－凝胶材料和介孔材料具有良好的光、热和化学稳定性，能改善客体分子的结构环境和化学微环境，从而能有效提高客体分子的发光性能。因此，本论文将具有优良近红外发光性能的稀土配合物分别与上述两种基质复合，从实验和理论研究稀土近红外发光杂化材料的性能和应用价值，制备出具有良好稳定性的高效稀土近红外发光杂化材料，以期为光纤通讯、激光等领域提供潜在的候选材料。围绕这一宗旨，开展了如下工作： 通过原位技术分别得到了掺杂和嫁接[Ln(dbm)3phen]化合物（Ln = Er, Nd, Yb）的杂化凝胶材料，Ln-D-P gel和Xerogel-Ln。通过对其近红外发光性能的研究，表明材料中配体能很好的保护稀土离子，并将能量有效的传递给稀土离子。采用Judd-Ofelt理论对所得部分材料进行了光谱分析，基于实验数据和理论分析表明其具有潜在的光放大和激光应用价值。 选择了两种含全氟化烷基链的β-二酮配体Hhfth和Htfnb，通过功能化的phen-Si配体，将三元配合物[Ln(hfth)3phen] (Ln = Er, Nd, Yb, Sm)和[Pr(tfnb)3phen]成功共价嫁接到介孔MCM-41和SBA-15杂化材料中，得到的衍生材料Ln(hfth)3phen–MCM-41、Pr(tfnb)3phen–MCM-41和Ln(hfth)3phen–SBA-15、Pr(tfnb)3phen–SBA-15都保持了高度有序的介孔p6mm结构，并展现出稀土离子特征的近红外发射。所得稀土配合物功能化的材料的发射光谱能完全覆盖对光通讯极具应用价值的1300-1600nm区域。 通过对Er(dbm)3phen–M41(X, Y) (X = 1~14, Y = 3, 6, 12, 18, 24 h)材料系统的比较研究，选择了X = 12, Y = 6作为合成目标材料的优化参数，通过功能化的phen-Si配体将[Ln(dbm)3phen]配合物共价嫁接于有序介孔MCM-41和SBA-15中(Ln = Er, Nd, Yb)，所得两类材料Ln(dbm)3phenM41和Ln(dbm)3phenS15都保持了很好的介孔有序性，并具有良好的近红外发光性能。通过对Ln(dbm)3phenM41和Ln(dbm)3phenS15两类材料发光行为的比较，以及两类材料中稀土离子的含量及孔结构的分析，推出以SBA-15为载体得到的材料在相对发光强度和荧光寿命上，均比以MCM-41为载体的材料有所提高。 通过对8－羟基喹啉配体进行改性，合成了具有双功能的配体Q-Si，继而合成了共价嫁接8－羟基喹啉衍生物的介孔杂化材料Q–SBA-15，其形貌均一，并具有高度有序的介孔p6mm结构。通过配体交换反应，得到了嫁接稀土喹啉配合物的具有近红外发光性能的介孔杂化材料LnQ3–SBA-15 (Ln = Er, Nd, Yb)，其仍然保持高度有序的介孔结构，且外形呈现与母体材料Q–SBA-15相似的弯曲圆柱状。激发配体的吸收，LnQ3–SBA-15材料都分别展现出相应稀土离子特征的近红外发射，并详细分析和讨论了所得介孔杂化材料的近红外发光性能。

吡唑酮衍生物的稀土配合物光致和电致发光性能研究

稀土配合物的发光具有发射带窄、色纯度高、峰发光位置不受配体环境变化的影响、发光不受温度影响等特点，而且发射峰覆盖400-1800纳米的可见区和近红外区，因此可以作为有机电致发光器件的发光层材料。现在的研究大多集中于铕、铽配合物的电致发光器件研究，对于近红外稀土配合物的电致发光以及发白光的镝配合物研究相对较少，但是近红外发光的稀土铒、钕、镱在光通讯、激光技术、生物医学、荧光探针等方面具有特殊的应用前景。在本论文中主要阐述了新型稀土配合物的设计与合成、在器件方面的应用以及器件结构机理的研究。 在本论文中，我们主要研究吡唑酮的衍生物配体对于稀土离子的敏化激发作用。通过配体基团的改性，得到发光更有效的新型稀土配合物。首先，合成了配体PM，并选择TP、Phen、Bipy、Bath做第二配体制备镝、铒、钕、镱、钐等的配合物。解析了配合物的晶体结构，测试得到了各种配合物的光致发光性能，系统分析了几种配合物中配体到中心稀土离子的能量传递过程，研究了配体对稀土的敏化机制。其中镝配合物显示近白光的发射，色坐标为x=0.35，y=0.40，以此配合物为发光层的器件显示明亮的白光，最大发光亮度为527cd/m2，是目前已经报道的镝配合物器件中，性能最突出的一个。 设计合成了配体PT、PC、PF，利用TP和Bath做中性配体与镱离子形成配合物YbPT3Bath、YbPT3TP、YbPC3Bath，它们都显示977纳米的近红外发射。经过分析发现，配体对镱离子的敏化过程是通过电子转移的机制来完成的。通过几种镱配合物发光强度对比发现YbPT3Bath、YbPC3Bath的发射最强。首先将YbPT3Bath用于电致发光器件中，发现其具有较好的电子传输特性，而且YbPM3TP2具有较好的空穴传输特性。因此，我们将这两种配合物结合制备了双发光层电致发光器件，得到的器件比单发光层器件的性能提升了若干倍。我们认为，双发光层器件结构改善了载流子的传输和最终的复合，使得激子在发光层内形成，提高激子激发发光层材料的效率。最后，利用这种双发光层器件结构得到了辐照度比较理想的镱配合物近红外器件。 对ErPM3TP2、NdPM3TP2配合物的发光性能做了系统研究。首先，分析了它们的晶体结构，得到了具体的晶体参数和结构组成。二者在紫外区的吸收光谱都显示为配体的吸收，在紫外区之后出现了稀土离子的特征吸收峰，由此我们利用Judd-Ofelt理论分析计算了Er3+、Nd3+离子在这个配位环境中的振子强度参数，最后得到Er3+、Nd3+离子从激发态能级到下能级的电偶极跃迁辐射几率以及相应的自然寿命值。利用这两种配合物做为发光层材料制备了系列近红外电致发光器件，得到理想的辐照度强度，证明它们在制备近红外器件方面具有潜在应用价值。

Spectroscopic properties of anisotropic absorption in a neodymium-doped YAlO3 laser crystal

Absorption spectra of YAlO3:Nd for the three crystallographic axes are investigated at room temperature, The spectral strengths indicate that the absorption coefficient of YAlO3:Nd is anisotropic. The anisotropy of the local electric field acting on the rare-earth ion in a laser crystal is considered, An extended Judd-Ofelt theory is applied to calculate the absorption cross sections and oscillator strengths of the electric-dipole transitions in the different principal directions. Three groups of the phenomenological parameters are derived from a least-squares-fitting procedure. We also analyze theoretically the anisotropy of the optical absorption of YAlO3:Nd crystal in detail. (C) 1997 American Institute of Physics.

Nd3+-doped LaF3 nanoparticles with a larger emission cross-section

A series of Nd3+-doped LaF3 nanoparticles with Nd3+ concentrations from 0.5 to 10 mol% were synthesized. The fluorescence intensity and lifetime of the nanoparticles at various Nd3+ doping concentration were investigated. The nanoparticles displayed strongest fluorescence intensity at 3 mol% Nd3+ concentration. Eighty-eight percentage quantum efficiency was obtained when the Nd3+ concentration was 0.5 mol%. Optical properties of nanoparticles were studied according to Judd-Ofelt theory. A larger emission cross-section, sigma(em), for F-4(3/2) -> I-4(11/2) transition of the Nd3+ ion was obtained as 3.21 x 10(-20) cm(2), which was two times of the currently reported value. The larger emission cross-section and strong fluorescence intensity demonstrate that these nanoparticles are promising materials for laser applications. (C) 2010 Published by Elsevier B. V.

System size dependence of associated yields in hadron-triggered jets STAR Collaboration

We present results on the system size dependence of high transverse momentum di-hadron correlations at root s(NN) = 200 GeV as measured by STAR at RHIC. Measurements in d + Au, Cu + Cu and Au + Au collisions reveal similar jet-like near-side correlation yields (correlations at small angular separation Delta phi similar to 0, Delta eta similar to 0) for all systems and centralities. Previous measurements have shown Chat the away-side (Delta phi similar to pi) yield is suppressed in heavy-ion collisions. We present measurements of the away-side Suppression as a function of transverse momentum and centrality in Cu + Cu and Au + Au collisions. The suppression is found to be similar in Cu + Cu and An + An collisions at a similar number of participants. The results are compared to theoretical calculations based on the patron quenching model and the modified fragmentation model. The observed differences between data and theory indicate that the correlated yields presented here will further constrain dynamic energy loss models and provide information about the dynamic density profile in heavy-ion collisions. (C) 2009 Elsevier B.V. All rights reserved.

Measurement of the Bottom Quark Contribution to Nonphotonic Electron Production in p plus p Collisions at root s=200 GeV

The contribution of B meson decays to nonphotonic electrons, which are mainly produced by the semileptonic decays of heavy-flavor mesons, in p + p collisions at root s = 200 GeV has been measured using azimuthal correlations between nonphotonic electrons and hadrons. The extracted B decay contribution is approximately 50% at a transverse momentum of p(T) >= 5 GeV/c. These measurements constrain the nuclear modification factor for electrons from B and D meson decays. The result indicates that B meson production in heavy ion collisions is also suppressed at high p(T).

Higher Moments of Net Proton Multiplicity Distributions at RHIC

200 GeV corresponding to baryon chemical potentials (mu(B)) between 200 and 20 MeV. Our measurements of the products kappa sigma(2) and S sigma, which can be related to theoretical calculations sensitive to baryon number susceptibilities and long-range correlations, are constant as functions of collision centrality. We compare these products with results from lattice QCD and various models without a critical point and study the root s(NN) dependence of kappa sigma(2). From the measurements at the three beam energies, we find no evidence for a critical point in the QCD phase diagram for mu(B) below 200 MeV.

Three-Particle Coincidence of the Long Range Pseudorapidity Correlation in High Energy Nucleus-Nucleus Collisions

We report the first three-particle coincidence measurement in pseudorapidity (Delta eta) between a high transverse momentum (p(perpendicular to)) trigger particle and two lower p(perpendicular to) associated particles within azimuth |Delta phi| < 0.7 in root s(NN) = 200 GeV d + Au and Au + Au collisions. Charge ordering properties are exploited to separate the jetlike component and the ridge (long range Delta eta correlation). The results indicate that the correlation of ridge particles are uniform not only with respect to the trigger particle but also between themselves event by event in our measured Delta eta. In addition, the production of the ridge appears to be uncorrelated to the presence of the narrow jetlike component.

gamma cross section in p plus p collisions at root s=200 GeV

We report on a measurement of the gamma(1S + 2S + 3S) -> e(+)e(-) cross section at midrapidity in p + p collisions at root s = 200 GeV. We find the cross section to be 114 +/- 38(stat + fit)(-24)(+23)(syst) pb. Perturbative QCD calculations at next-to-leading order in the color evaporation model are in agreement with our measurement, while calculations in the color singlet model underestimate it by 2 sigma. Our result is consistent with the trend seen in world data as a function of the center-of-mass energy of the collision and extends the availability of gamma data to RHIC energies. The dielectron continuum in the invariant-mass range near the gamma is also studied to obtain a combined yield of e(+)e(-) pairs from the sum of the Drell-Yan process and b-(b) over bar production.

Parton energy loss in heavy-ion collisions via direct-photon and charged-particle azimuthal correlations

Charged-particle spectra associated with direct photon (gamma(dir)) and pi(0) are measured in p + p and Au + Au collisions at center-of-mass energy root(S)(NN) = 200 GeV with the STAR detector at the Relativistic Heavy Ion Collider. A shower-shape analysis is used to partially discriminate between gamma(dir) and pi(0). Assuming no associated charged particles in the gamma(dir) direction ( near side) and small contribution from fragmentation photons (gamma(frag)), the associated charged-particle yields opposite to gamma(dir) (away side) are extracted. In central Au + Au collisions, the charged-particle yields at midrapidity (vertical bar eta vertical bar < 1) and high transverse momentum (3 < (assoc)(PT) < 16 GeV/c) associated with gamma(dir) and pi(0) (vertical bar eta vertical bar < 0.9, 8 < (trig)(PT) < 16 GeV/c) are suppressed by a factor of 3-5 compared with p + p collisions. The observed suppression of the associated charged particles is similar for gamma(dir) and pi(0) and independent of the gamma(dir) energy within uncertainties. These measurements indicate that, in the kinematic range covered and within our current experimental uncertainties, the parton energy loss shows no sensitivity to the parton initial energy, path length, or color charge.

Azimuthal di-hadron correlations in d plus Au and Au plus Au collisions at root s(NN)=200 GeV measured at the STAR detector

Yields, correlation shapes, and mean transverse momenta p(T) of charged particles associated with intermediate-to high-p(T) trigger particles (2.5 < p(T) < 10 GeV/c) in d + Au and Au + Au collisions at root s(NN) = 200 GeV are presented. For associated particles at higher p(T) greater than or similar to 2.5 GeV/c, narrow correlation peaks are seen in d + Au and Au + Au, indicating that the main production mechanism is jet fragmentation. At lower associated particle pT < 2 GeV/c, a large enhancement of the near- (Delta phi similar to 0) and away-side (Delta phi similar to pi) associated yields is found, together with a strong broadening of the away-side azimuthal distributions in Au + Au collisions compared to d + Au measurements, suggesting that other particle production mechanisms play a role. This is further supported by the observed significant softening of the away-side associated particle yield distribution at Delta phi similar to pi in central Au + Au collisions.

Balance functions from Au+Au, d+Au, and p+p collisions at root s(NN)=200 GeV

Balance functions have been measured for charged-particle pairs, identified charged-pion pairs, and identified charged-kaon pairs in Au + Au, d + Au, and p + p collisions at root s(NN) = 200 GeV at the Relativistic Heavy Ion Collider using the STAR detector. These balance functions are presented in terms of relative pseudorapidity, Delta eta, relative rapidity, Delta y, relative azimuthal angle, Delta phi, and invariant relative momentum, q(inv). For charged-particle pairs, the width of the balance function in terms of Delta eta scales smoothly with the number of participating nucleons, while HIJING and UrQMD model calculations show no dependence on centrality or system size. For charged-particle and charged-pion pairs, the balance functions widths in terms of Delta eta and Delta y are narrower in central Au + Au collisions than in peripheral collisions. The width for central collisions is consistent with thermal blast-wave models where the balancing charges are highly correlated in coordinate space at breakup. This strong correlation might be explained by either delayed hadronization or limited diffusion during the reaction. Furthermore, the narrowing trend is consistent with the lower kinetic temperatures inherent to more central collisions. In contrast, the width of the balance function for charged-kaon pairs in terms of Delta y shows little centrality dependence, which may signal a different production mechanism for kaons. The widths of the balance functions for charged pions and kaons in terms of q(inv) narrow in central collisions compared to peripheral collisions, which may be driven by the change in the kinetic temperature.