Probe Raman Spectroscopy of Uranyl-Compound Polycrystals

Optics and Spectroscopy - Regularities in the Raman spectra of acetate uranyl compounds CsUO2(CH3COO)3, CsUO2(CD3COO)3, NaUO2(CH3COO)3, NaUO2(CD3COO)3, UO2(CH3COO)2, and RbUO2(CH3COO)3 have been...     

Ultraviolet upconversion fluorescence in rare-earth-ion-doped Y2O3 induced by infrared diode laser excitation

Room-temperature ultraviolet emission of Tm(3+) ions at 298 ((1)I(6)-->(3)H(6)), 364 ((1)D(2)-->(3)H(6)), and 391 nm ((1)I(6)-->(3)H(5)) was obtained in Y(2)O(3):Yb(3+)-Tm(3+) by continuous-wave diode laser excitation of 980 nm. Power dependence analysis demonstrates that five- and six-photon upconversion processes populate the (1)D(2) and (1)I(6) states, respectively. We believe that the (1)D(2) population originates from the cross relaxation (1)G(4)+(3)F(4)-->(3)H(4)+(1)D(2) of the Tm(3+) ions, while subsequent energy transfer from Yb(3+) to Tm(3+) excites the (1)D(2) state to the upper (1)I(6) state. High multiphoton-induced ultraviolet emission is also expected for other trivalent rare-earth ions similar to Tm(3+).     

Ultrasound-promoted preparation of disteryl ethers catalyzed by montmorillonite K 10

In the presence of montmorillonite K 10, 5(6)-unsaturated sterols (1) were heated under ultrasound at 45 degrees C in dichloromethane for 2-5.5 h to provide 3 beta,3'beta-5(6)/5'(6')-unsaturated disteryl ethers (2) in 35-79% yield. Meanwhile, 3 alpha,3'alpha-diandrost-5-en-17-one-3-yl ether (3a) and 3 alpha,3'alpha-dipregn-5-en-20-one-3-yl ether (3b) were also obtained as by-products from 3 beta-hydroxyl-androst-5-en-17-one (1a) and 3 beta-hydroxyl-pregnan-5-en-20-one (1b) respectively.     

(Y,Gd)Al3(BO3)4:Tb的真空紫外光谱特性

(Y,Gd)Al3(BO3)4属于三角晶系,具有R32的空间群,掺入Ce3 ,Tb3 杂质后,其晶格结构没有变化。(Y,Gd)Al3(BO3)4:Tb随着Gd3 摩尔浓度增大,基质吸收带红移。Gd3 和Tb3 之间存在着很有效的能量传递。Gd3 摩尔浓度在一定范围内(0~0·75mol)增大时,样品在120~300nm光谱范围内的激发强度均是增强的;但是,Gd3 浓度过高造成Gd3 的发射增强,GdAl3(BO3)4:Tb在120~240nm光谱范围内激发强度很明显下降。(Y,Gd)Al3(BO3)4:Ce,Tb在真空紫外激发下,发现Tb3 的发光明显的被Ce3 猝灭。     

Room temperature oxidation of Cu(3)Ge films grown on Si and Si(1-x)Ge(x) substrates

Room temperature oxidation of Cu3Ge films grown on Si, Si(0.85)Ge(0.15) and Si(0.52)Ge(0.48) substrates, respectively, at a temperature of 200-300 degrees C was studied using transmission electron microscopy (TEM) in conjunction with energy dispersive spectrometry (EDS) and scanning electron microscopy (SEM). For Cu(3)Ge films grown at 200 degrees C and subsequently exposed in air for 1 week oxide protrusions and oxide networks appeared in the film surface and grain boundaries of Cu(3)Ge, respectively. At room temperature O from air and Si from the substrate, diffused along the grain boundaries of Cu(3)Ge to react with Cu(3)Ge grains, initiating the Cu(3)Si-catalyzed oxidation. Cu(3)Ge films are superior to Cu(3)(Si(1-x)Gex) films in retarding Cu(3)Si-catalyzed oxidation. Annealing at 300 degrees C allowed Si diffusion from the substrate into the Cu(3)Ge overlayer to form Cu(3)(Si(1-x)Gex), enhancing the Cu(3)Si-catalyzed oxidation rate. In the present study, Cu(3)Ge films grown on Si(0.52)Ge(0.48) at 200 degrees C show the best resistance to room temperature oxidation because higher Ge concentration in the substrate and lower temperature annealing can more effectively retard Si diffusion from the substrate into the Cu(3)Ge overlayer, and hence reduce the Cu(3)Si-catalyzed oxidation rate.     

(La,Ce,Tb)BO3的合成及光谱性质

采用高温固相法合成了(La,Ce,Tb)BO₃绿色发光粉,并对该发光粉进行了XRD和SEM分析。结果表明:(La,Ce,Tb)BO₃的晶体结构和LaBO₃相同,Ce³⁺、Tb³⁺的掺入并没有改变晶体的结构,发光粉颗粒大小均匀,形貌规则,粒度在5 μm左右。研究了(La,Ce,Tb)BO₃的光谱性质,在(La,Ce,Tb)BO₃的发射和激发光谱中除了有Tb³⁺的特征发射和激发峰外,还有Ce³⁺的特征发射和激发峰。比较了(La,Ce)BO₃发射光谱和(La,Tb)BO₃的激发光谱,两者存在重叠,这为Ce³⁺→Tb³⁺的能量传递提供了条件。将(La,Ce,Tb)BO₃的发射光谱与商品粉(La,Ce,Tb)PO₄进行比较,两者的发射主峰都在541 nm处, (La,Ce,Tb)BO₃在489 nm处的峰位稍有红移,通过计算表明,(La,Ce,Tb)BO₃的发光亮度达到商品粉(La,Ce,Tb)PO₄的94.7%。因此,(La,Ce,Tb)BO₃是一种很有应用前景的绿色发光粉。     

5f electron localization-delocalization transition from UPd3 to UPt3

The electronic structures of URh (3), UPd (3), UPt (3), and UAu (3) are calculated with the self-interaction corrected local-spin-density approximation. We find that only in URh (3) the f electrons are fully delocalized. UPt (3) has one f electron localized at each U site, while a localized f(2) configuration of the U ion is found for UPd (3). It is predicted that, upon application of a pressure of 25 GPa, UPd (3) will acquire the f(1) configuration and possibly exhibit heavy-fermion behavior. We find that UAu (3) is characterized by the same mixed localized-delocalized f-electron manifold as UPd (3).     

惰性离子(La3+,Y3+,Gd3+)对配合物苯乙酮酸邻菲咯啉铕荧光性能的影响

以苯乙酮酸和邻菲咯啉为配体,不同摩尔比铕和惰性离子(La3 ,Y3 ,Gd3 )为中心离子,合成了系列配合物EuxRE1-xL3phen(RE=La,Y,Gd),测定了其荧光激发光谱和荧光发射光谱,研究了惰性离子(La3 ,Y3 ,Gd3 )对Eu3 荧光性能的影响.结果表明,配合物激发光谱相似,均在350～360 nm范围内出现最大激发,属于配体的吸收峰,在398 nm附近出现弱的激发为Eu3 的吸收峰;系列配合物荧光发射光谱相似,均显示Eu3 离子的特征发射光谱,位于583,595,617,654,703 nm附近出现5组强度不同的发射峰,分别归属为Eu3 的5D0-7F0,5D0-7F1,5D0-7F2,5D0-7F3,5D0-7F4能级跃迁.发射光谱表明,系列配合物中La3 离子对Eu3 的荧光发射峰峰位影响最大,EuxLa1-xL3phen中La3 的摩尔分数为0.7时,Eu3 的5D0-7F2跃迁可改变5.2 nm,而Y3 和Gd3 对Eu3 的荧光发射峰峰位影响较弱,配合物EuxY1-xL3phen和EuxGd1-xL3phen中Eu3 的荧光发射峰位变化较小,最大时仅改变2 nm;发射光谱强度表明,La3 对Eu3 的荧光发射影响最大,EuxLa1-xL3phen中La3 含量为0.7时,可使其相对荧光强度增大2倍以上,对其具有很好的敏化作用.这对人们寻找发光性能好、价格便宜的发光材料提供了理论依据.     

Three-Quark Potential in SU(3) Lattice QCD

The static three-quark ( 3Q) potential is studied in SU(3) lattice QCD with 12(3)x24 and beta = 5.7 at the quenched level. From the 3Q Wilson loop, 3Q ground-state potential V(3Q) is extracted using the smearing technique for ground-state enhancement. With accuracy better than a few percent, V(3Q) is well described by a sum of a constant, the two-body Coulomb term, and the three-body linear confinement term sigma(3Q)L(min), with L(min) the minimal value of total length of color flux tubes linking the three quarks. Comparing with the Q-&Qmacr; potential, we find a universal feature of the string tension, sigma(3Q) approximately sigma(Q&Qmacr;), and the OGE result for Coulomb coefficients, A(3Q) approximately 1 / 2A(Q&Qmacr;).     

W-parity, octet dominance and the breaking of chiral symmetry

It is shown that W-invariance together with octet dominance restricts the SU(3) × SU(3) symmetry breaking Lagrangian to the representations (3, ) ( ,3), (6, ) ( ,6), (8,8) and (1,8) (8,1). In a nonlinear model, this Lagrangian predicts that the T = 2, S-wave π-π scattering length is zero; and when fitted to the empirical pion and K-meson masses, it predicts a T = 0 scattering length of 0.26m_π⁻¹. Compared with the (3, ) ( ,3) model, this model gives a larger (by a factor 8/3) nucleon σ-term, in agreement with recent calculations.     

Ultraviolet upconversion emissions of Gd3+

Under 980 nm excitation, upconversion (UC) emissions in the UV range of 270-320 nm were observed in nanocrystals Y(0.795-x)Gd(x)Yb(0.2)Tm(0.005)F(3) (x=0, 0.1, 0.2, 0.5, and 0.795), which were synthesized through a hydrothermal method. These UC emissions can be assigned to the transitions of (6)I(J), (6)P(J)-->(8)S(7/2)(Gd(3+)), and (3)P(0)/(1)I(6)-->(3)H(6) (Tm(3+)). The energy transfer from Tm(3+) to Gd(3+) plays a crucial role in populating the excited states of Gd(3+). The shortest wavelength of upconverted emission converted from the infrared region was demonstrated here.     

14N chemical shifts and quadrupole coupling constants of inorganic nitrates

The isotropic chemical shift and the nuclear quadrupole coupling constant for (14)N were obtained for 14 inorganic nitrates by solid-state MAS NMR measurements at two different field strengths, 9.4 and 11.7 T. The compounds studied were polycrystalline powders of AgNO(3), Al(NO(3))(3), Ba(NO(3))(2), Ca(NO(3))(2), CsNO(3), KNO(3), LiNO(3), Mg(NO(3))(2), NaNO(3), Pb(NO(3))(2), RbNO(3), Sr(NO(3))(2), Th(NO(3))(4)center dot4H(2)O, and UO(2)(NO(3))(2)center dot3H(2)O. Even though the spectra show broadening due to (14)N quadrupole interactions, linewidths of a few hundred hertz and a good signal-to-noise ratio were achieved. From the position of the central peaks at the two fields, the chemical shifts and the nuclear quadrupole coupling constants were calculated. The chemical shifts for all compounds studied range from 282 to 342 ppm with respect to NH(4)Cl. The nuclear quadrupole coupling constants range from 429 kHz for AgNO(3) to 993 kHz for LiNO(3). These data are compared with those available in the literature.     

不同方法制备的CO2-3替换磷灰石固溶体晶体化学的FTIR研究

采用不同方法制备了CO2-3替换的磷灰石固溶体,利用FTIR结合XRD对其进行了晶体化学研究,结果表明均相沉淀法制备的碳羟磷灰石(CHAP)属B型替换且替换方式是[CO3·OH]四面体替换[PO4]四面体;固相离子交换法制备的CHAP属A型替换且替换方式是[CO3]三角形配位体替换通道位置的OH-;固相反应法制备的碳氟磷灰石(CFAP)属B型替换,其替换方式是[CO3·F]四面体替换[PO4]四面体;sol-gel法制备的CHAP属AB混合型替换,其Ψ3分裂为Ψ3-1,Ψ3F,Ψ3-4.高斯函数法拟合表明Ψ3F峰是A型替换的Ψ3-2与B型替换的Ψ3-3的叠合.当WCO2-3＜3.34%时,随CO2-3含量增加,A型替换量增大,且当WCO2-3=3.34%时达最大值,当3.34%＜WCO2-3＜7.52%时,随CO2-3含量增加,B型替换量增大,且当WCO2-3= 7.52%时亦到饱和.     

Ca9R(VO4)7 : Eu3+ 发光粉的发光特性

采用高温固相法制备了Eu³⁺离子激活的Ca₉R(VO₄)₇(R = Y, La, Gd)红色发光粉,并利用荧光光谱对发光粉的特性进行研究。激发光谱中,Ca₉Y(VO₄)₇ : Eu³⁺ , Ca₉La(VO₄)₇ : Eu³⁺和Ca₉Gd(VO₄)₇ : Eu³⁺都有两个宽的VO^3-₄激发带和Eu³⁺的特征激发峰。发射光谱中,在Ca₉Y(VO₄)₇ : Eu³⁺ 和Ca₉La(VO₄)₇ : Eu³⁺中的350~550 nm范围内出现VO^3-₄的发射带,而在Ca₉Gd(VO₄)₇ : Eu³⁺中却没有观察到VO^3-₄的发射。在这三种发光粉中,Ca₉Gd(VO₄)₇ : Eu³⁺的发光强度远远高于其它两种,这是由于Gd³⁺的存在有效地使能量通过Gd³⁺ →VO^3-₄ → Eu³⁺及Gd³⁺ → Eu³⁺的两种方式进行能量传递,从而提高了Eu³⁺发光效率。     

Ultrasonic-assisted synthesis of highly dispersed MoO3 nanospheres using 3-mercaptopropyltrimethoxysilane

With ultrasonic irradiation as assistance, highly dispersed MoO(3) nanospheres were synthesized using silane coupling agent 3-mercaptopropyltrimethoxysilane HS-(CH(2))(3)Si(OCH(3))(3) (MPTS) as figuration agent. The results of X-ray powder diffractometer (XRD) showed that the precursor was hexagonal molybdenum oxide hydrate (MoO(3).0.55H(2)O). It was converted into orthorhombic MoO(3) after annealed at 400 degrees C for 2h. Transmission electron microscopy (TEM) showed that MoO(3).0.55H(2)O and MoO(3) nanoparticles were spherical with particle-size distribution of ca. 30-80 nm and 25-75 nm, respectively. Results indicated that MPTS and ultrasonic irradiation played important role in formation of highly dispersed MoO(3) nanospheres. X-ray photoelectron spectroscopy (XPS) was also adopted to confirm the growth mechanism. The possible cause of formation was based on dispersion function of ultrasonic irradiation and figuration of MPTS.     

Excited-configuration metastable level lifetimes of Cl-like Mn IX and Fe X

Forbidden transitions from levels with 3P and 1D cores in excited configurations of Cl-like Mn IX and Fe X have been isolated using interference filters. The fluorescence decay lifetimes of ions orbiting in a Kingdon ion trap were measured. New relativistic configuration interaction calculations of relevant level lifetimes, to aid the analysis, based on B-spline basis sets, are also presented. Line identifications and experimental lifetimes are Mn IX ((4)D(7/2)-(4)F(9/2)):363(-3/+7) nm; tau(Mn IX3p(4)(3P)3d (4)F(9/2)) = 210+/-42 ms; tau(Fe X,3p(4)(3P)3d (4)F(9/2)) = 85.7+/-9.2 ms; tau(Fe X,3p(4)(3P)3d (4)F(7/2)) = 93+/-30 ms; and tau(Fe X, 3p(4)(1D)3d (2)G(9/2)) = 17.8+/-3.1 ms.     

2-(4-氯代苯甲酰基)苯甲酸配合物光致发光研究

以Eu3+,Tb3+为中心离子,2-(4-氯代苯甲酰基)苯甲酸(HCBBA)为第一配体,邻菲咯啉(Phen)、三苯基氧膦(TPPO)、二苯亚砜(DPSO)为第二配体,合成了多种铕铽的二元和三元配合物,并测试其荧光效能,以研究配体的加入对中心离子发光强度的影响。结果表明,合成的配合物均发出Eu(Ⅲ)和Tb(Ⅲ)的特征荧光,但相对强度明显不同。在铕与2-(4-氯代苯甲酰基)苯甲酸根(CBBA)形成的配合物体系中,Phen和DPSO显示了较强的敏化作用,且Phen敏化效果更强,而TPPO则对配合物荧光有猝灭作用。在Tb-CBBA体系中,DPSO表现出很强的敏化作用, Phen和TPPO却对配合物荧光起猝灭作用,且TPPO猝灭效果更强。经红外推测,羧酸根均以双齿桥式与Eu3+和Tb3+配位;在3 200～3 600 cm-1出现水的弱的羟基的伸缩振动吸收峰,表明配合物中含有结晶水。     

Local Structure Analysis of Lead Zinc Niobate-Barium Titanate Ceramic by X-Ray Absorption Spectroscopy and Density Functional Calculation

The local structure of an alternative Pb(Zn_(1/3)Nb_(2/3))O3-based perovskite ceramic is investigated. The 0.07 BaTiO_3-0.93 Pb(Zn_(1/3)Nb_(2/3))O_3 ceramic is synthesized using a combination of Zn_3 Nb_2 O_8 B-site precursor and BaTiO_3 perovskite phase stabilizer. Then, x-ray absorption spectroscopy and density functional theory are employed to calculate the local structure configuration and formation energy of the prepared samples. Ba2+ is found to replace_Pb)~(2+) in A-site with Zn~(2+) occupying B-site in Pb(2 n_(1/3)Nb_(2/3))O_3, while in the neighboring structure, Ti~(4+)replaces Nb~(5+) in B-site with Pb~(2+) occupying A-site. With the substitution of BaTiO_3 in Pb(Zn_(1/3)Nb_(2/3))O_3, the bond length between Zn2+ and Pb~(2+) is longer than that of the typical perovskite phase of Pb(Zn_(1/3)Nb_(2/3))O_3.This indicates the key role of BaTiO_3 in decreasing the steric hindrance of Pb~(2+) lone pair, and the mutual interactions between Pb~(2+) lone pair and Zn2+ and the formation energy is seen to decrease. This finding of the formation energy and local structure configuration relationship can further extend a fundamental understanding of the role of BaTiO_3 in stabilizing the perovskite phase in PbZn_(1/3)Nb_(2/3)O_3-based materials,which in turn will lead to an improved preparation technique for desired electrical properties.     

[Au(PH_3)]~+芳香基发光材料的光谱性质研究

用二阶微扰(MP2)法和单激发组态相互作用(CIS)法分别优化了发光材料H3PAuPh和(H3PAu)2(1,4-C6H4)2的基态和激发态的几何结构,并用含时密度泛函(TD-DFT)法计算了各发光材料的吸收光谱与磷光发射光谱。计算结果表明,H3PAuPh和(H3PAu)2(1,4-C6H4)2的磷光发射光谱均具有在Au(6p)→C(2p)的金属向配体的电荷转移(MLCT)参与下的pπ*(Ph)→pπ(Ph)跃迁的本质,并伴有Au(6p)→Au(5d)的金属中心电荷转移(MCCT)的性质。(H3PAu)2(1,4-C6H4)2是由两个H3PAuPh连接而成的。因此(H3PAu)2(1,4-C6H4)2的分子轨道也是由H3PAuPh的分子轨道组合而成的。在磷光发射中,由于轨道组合中存在pπ*或pπ的相互作用,所以(H3PAu)2(1,4-C6H4)2的最低能量磷光发射光谱谱线的波长大于H3PAuPh的相应值。     

二氧六环参与配位的稀土配合物的制备和荧光性能研究

利用二氧六环(dioxane)小分子作为第二配体,吡哌酸(PPA)作为第一配体合成了稀土荧光配合物Eu(PPA)3dioxane和Tb(PPA)sdioxane.这种小分子直接参与配位形成稀土配合物的现象很少见到.所合成的配合物通过与单独使用吡哌酸作为配体的配合物Eu(PPA)3和Tb(PPA)3对比,发现二氧六环对稀土配合物的荧光具有明显的增强效果,尤其是对Tb3+所形成的稀土配合物,荧光增强非常显著.二氧六环的参与配位,代替了原来的水分子,这样就会在一定程度上减少了热振动所造成的能壁损失,从而增强荧光.所制备的稀土配合物通过红外光谱、荧光光谱、荧光寿命等方法进行了表征.对于由Eu和Tb所形成的配合物,加入第二配体二氧六环对其荧光寿命的影响差别很大,这说明对于Eu和Tb所形成的配合物存在着不同的能鸶传递过程.这种荧光增强现象为检测小分子二氧六环的存在及其含量提供了一种新的方法.