Optical limiting characteristics of Dichloridobis(1-ethyl-2, 6-dimethylpyridinium-4-olate-κO) zinc (II)

A newly synthesized metal-organic co-ordination compound Dichloridobis (1-ethyl-2,6-dimethylpyridinium-4-olate-κO) zinc(II) (EDMPZC) is characterized by FTIR to confirm the molecular structure. It crystallizes in the monoclinic system with the centrosymmetric space group C2/c and the unit cell parameters are determined from the single crystal X-ray diffraction analysis. Optical energy band gap is found to be 3.5 eV by UV-Visible absorption studies. The third order nonlinear optical properties were investigated by open-aperture Z-scan measurements using Nd:YAG laser (532 nm, 5 ns). Two-photon absorption and reverse saturable absorption mechanisms at the excitation wavelength are found to cause the observed optical limiting behavior.     

Photoluminescent properties of di(8-hydroxyquinolato) zinc impregnated in nanoporous glass

Photoluminescent properties of a metal-organic complex, di(8-hydroxyquinolato) zinc, impregnated in nanoporous glass were investigated. In comparison with those in the normal organic fluorescent material, the emission band of the impregnated organic phosphor became wider. Blueshift (14 nm) was observed due to π*→n emission transition. The excitation band of the embedded organic phosphor had a larger blueshift and was divided into several sub-bands. The intensity in the short wavelength end of the embedded organic fluorescent material became much stronger.     

SU(4)×SU(4)禁闭弱作用复合模型

本文对超色群为半单群的亚夸克模型结构作了讨论, 具体构造了一个SU(4)×SU(4)禁闭弱作用复合模型, 模型中给出了三代轻质量的复合粒子.     

有机材料(EDT-DSDTFVO)FeCl_4和(EDT-DSDTFVO)GaCl_4的输送现象

通过对有机材料(EDT-DSDTFVO)2FeCl4和(EDT-DSDTFVO)2GaCl4的输送测定,对其电阻率的温度依赖性以及压力效果进行了系统的比较,虽然两类盐的电阻率随着温度的变化行为十分相似,但是其压力效果尤其在高压时表现出明显的差异性。认为这种差异性和π-d相互作用密切相关。在这里,用EDT-DSDTFVO表示ethylenedithiodiselenadithiafulvalenothioquinone-1,3-dithiole methide。     

N(~4S_u) CH(a~4∑~-)体系的分子反应动力学研究

用轨线法对Ｎ（４Ｓｕ）＋ＣＨ（０，０）→ＣＮ（ｖ′，Ｊ′）＋Ｈ（２Ｓｇ）和Ｎ（４Ｓｕ）＋ＣＨ（０，０）→ＮＨ（ｖ′，Ｊ′）＋Ｃ（３Ｐｇ）反应进行计算，研究了两个反应的阈能、反应截面、产物散射分析和微观反应机理     

有机材料(EDT-DSDTFVO)FeCl4和(EDT-DSDTFVO)GaCl4的磁电阻分析

有机材料(EDT-DSDTFVO)2FeCl4和(EDT-DSDTFVO)2GaCl4的输送实验结果,显示出这两类盐的电阻率对温度的依赖性以及压力效果十分相似,但是两种盐的磁电阻率却表现出很大的不同,FeCl4盐为负磁电阻,而GaCl4盐为正磁电阻.我们认为这种输送现象的差异性起源于π-d相互作用.我们用EDT-DSDTFVO表示ethylenedithiodiselenadithiafulvalenothioquinone-1,3-dithiole methide.     

Na5Eu(MoO4)4和Na5Eu(WO4)4的荧光光谱和晶场参数

本文报告了Na5Eu(MoO4)4和Na5Eu(WO4)4粉末样品的荧光光谱。结果表明,在这些化合物中,稀土离子占据S4对称性晶格点,点对称性相当接近D2d。从实验光谱数据,我们导出了D2d对称性下Na5Eu(MoO4)和Na5Eu(WO4)4的晶场参数,这些参数相当好地拟合了从光谱实验中得到的能级。     

Similarities in the decomposition and dehydrogenation of cyclohexene on (4 × 4)-CMo(110) and Pt(111)

The decomposition and dehydrogenation of cyclohexene have been used as probing reactions to directly compare the surface reactivities of carbon-modified Mo(110) and Pt(111). By using temperature programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS), we find that the dominant decomposition pathway of cyclohexene can be converted from complete decomposition to atomic carbon and hydrogen on clean Mo(110) to partial dehydrogenation to benzene and hydrogen on (4 × 4)-CMo(110). The latter reaction mechanism is very similar to that observed on Pt(111). Furthermore, in contrast to the near identical catalytic properties that are commonly observed for bulk molybdenum carbide and nitride powder materials, we find that the reactivities of carbon-modified and nitrogen-modified Mo(110) surfaces are qualitatively different.     

SUPERCONDUCTIVITY IN La_(1.85)Sr_(0.15)Cu_(1-x)Zn_xO_4

Based on the multiple exchange-mediated interaction mechanism of high- Tc superconductivity and the Abrikosov-Gorkov theory of magnetic impurity superconductors, this paper quantitatively explains the Zn-substitution experiment of La1.85Sr0.15Cu1-x ZnxO4.     

掺杂晶体(NH_4)_(1-x)K_xNO_3、(NH_4)_(1-x)Na_xNO_3振动模的临界行为

掺杂晶体（ＮＨ４）１－ｘＫｘＮＯ３、（ＮＨ４）１－ｘＮａｘＮＯ３振动模的临界行为王焕茹吴国祯（清华大学物理系北京１０００８４）ＴｈｅＣｒｉｔｉｃａｌＢｅｈａｖｉｏｕｒｓｏｆｔｈｅＶｉｂｒａｔｉｏｎａｌＭｏｄｅｓｏｆＤｏｐｅｄ（ＮＨ４）１－ｘＫｘＮＯ...     

LD泵浦Nd~(3 )∶GdVO_4/Cr~(4 )∶YAG固体激光器

通过合理设计,精密调控各元件和温控电流,得到了平均功率为70mW,脉冲宽度为22ns,重复频率为14kHz,峰值功率高达230W的Nd3 ∶GdVO4/Cr4 YAG绿光脉冲激光器·腔外采用望远镜系统聚焦,经KTP晶体倍频后,得到了平均功率为28.8mW,脉冲宽度为19ns,重复频率为14kHz,峰值功率高达108W的绿光激光输出,转换效率高达·指出了小光斑对倍频晶体带来的影响·     

基质发光材料Na5Eu(MoO4)4和NaEu(MoO4)2的制备和发光

本文研究了化学计量的基质发光材料Na5Eu(MoO4)4和NaEu(MoO4)2.它们都属于四方晶系,空间群为I41/α .NaEu(Mo04)2属于白钨矿(scheelite)结构,一个晶胞中有2个分子式NaEu(MoO4)2(z=2);而Na5Eu(Mo4O)4属于类自钨矿(scheelite-like)结构,一个晶胞中有4个分子式Na5Eu(MoO4)4(z=4).X射线衍射确定的晶胞常数,对Na5Eu(MoO4)4,α=1.1439nm和c=1.1486nm(密度d计算=4.01g/cm3,z=4);对NaEu(MoO4)2,α=0.5236nm和c=1.1439nm(密度d计算=5.24g/cm3,z=2).由差热法和X射线衍射法确定了Na2MoO4-Eu2(MoO4)3的相图.Na5Eu(MoO4)4分解为NaEu(MoO4)2的温度是700℃.本文确定了制备纯 Na5Eu(MoO4)和NaEu(MoO4)2的方法,并研究了上述两种材料的激发光谱和发光光谱.确定了用X射线粉末衍射谱和发光光谱鉴别Na5Eu(MoO4)4和NaEu(MoO4)2的方法.在365nm紫外光激发下,Na5Eu(MoO4)4的发光比Na5Eu(WO4)4的强得多,在室温下,Na5Eu(MoO4)4,NaEu(MoO4)2和Na5Eu(WO4)4的相对发光积分亮度比为3.8:3.2:1.0.     

水热法制备的NaEu(MoO_4)_(2-x)0(WO_4)_x固溶体微晶及其发光特性

采用水热法制备了NaEu(MoO4)2-x(WO4)x固溶体微晶;通过X射线衍射(XRD)、扫描电镜(SEM)和荧光分析(FA)对所制备的微晶进行了表征。XRD结果表明NaEu(MoO4)2-x(WO4)x微晶呈现典型的四方晶相白钨矿结构。SEM分析表明微晶呈米粒状。荧光分析显示,NaEu(MoO4)2-x(WO4)x微晶在370~386 nm之间呈现MO2-4配离子(M=Mo,W)的特征发射峰,发射波长随x的增大而减小;同时,Eu3+在592 nm(5D0→7F1)和614 nm(5D0→7F2)的特征发射峰均明显显现,强度随x的增大而逐渐增大。     

基质发光材料Na5Eu(MoO4)4和NaEu(MoO4)2的喇曼光谱

本文研究了基质发光材料Na5Eu(MoO4)4和NaEu(MoO4)2的喇曼光谱.用群论方法分析了它们的内、外振动模式,对实验振动模进行了指认.本文还将上述喇曼光谱与Na5Eu(WO4)4、CaWO4、SrWO4、CaMoO4和SrMoO4的喇曼光谱进行了比较,Na5Eu(MoO4)4和NaEu(MoO4)2的喇曼光谱结果表明(MoO4)2-离子团的高能量拉伸内振动是产生Eu3+的5D2→5D1,5D1→5D0-多声子无辐射弛豫的原因,这导致了Eu3+在这类材料中主要产生5DO→7Fj的发光跃迁.     

Low-temperature phase transitions and dynamics of ammonium in (NH4)3H(SO4)2 and [(NH4)1−x Rbx]3H(SO4)2 crystals

The (NH₄)₃H(SO₄)₂ and [(NH₄)_0.82Rb_0.18]₃H(SO₄)₂ crystals are investigated by dielectric spectroscopy, inelastic incoherent neutron scattering (IINS), and neutron powder diffraction. A comparative analysis of the data obtained is given. It is shown that the phase transitions II ? III, III ? IV, IV ? V, and V ? VII in the (NH₄)₃H(SO₄)₂ crystal are accompanied by changes in the orientation ordering of the NH ₄ ⁺ ions. In the [(NH₄)_0.82Rb_0.18]₃H(SO₄)₂ crystal, these phase transitions are completely suppressed and the long-range order inherent in the II phase is retained over the entire temperature range covered (6–300 K). It is revealed that this crystal at the temperature T _g≈70 K undergoes a transition to the dipole glass phase, which is attended by “freezing” the orientation disordering of the ammonium ions.     

Optical absorption of zinc selenide doped with cobalt (Zn1−xCoxSe) under hydrostatic pressure

Abstract

The optical absorption of the diluted magnetic semiconductor Zn_1?xCO_xSe (x = 0.02) has been measured at room temperature under hydrostatic pressure up to 14GPa in a membrane diamond-anvil cell. We found two absorption features: (i) an absorption structure in the energy range 1.6?1.8eV, with a negligible pressure shift (i.e., 0.45 ± 0.05 meV/GPa) which we have identified as the Co²⁺(3d⁷) internal transition ⁴A₂(F)→+⁴T₁(P) and (ii) an onset in the energy range 2?2.7eV which redshifts with pressure (?8.1±0.6meV/GPa). We have attributed such absorption edge to charge transfer between the ZnSe valence band and the Co²⁺(3d⁷) levels.     

Critical (Φ4)3,ε

The Euclidean (⁴)_3, model in R³ corresponds to a perturbation by a ⁴ interaction of a Gaussian measure on scalar fields with a covariance depending on a real parameter in the range 01. For =1 one recovers the covariance of a massless scalar field in R³. For =0, ⁴ is a marginal interaction. For 0<1 the covariance continues to be Osterwalder-Schrader and pointwise positive. We consider the infinite volume critical theory with a fixed ultraviolet cutoff at the unit length scale and we prove that for >0, sufficiently small, there exists a non-gaussian fixed point (with one unstable direction) of the Renormalization Group iterations. We construct the stable critical manifold near this fixed point and prove that under Renormalization Group iterations the critical theories converge to the fixed point. Partially supported by NSERC of CanadaLaboratoire Associé au CNRS. UMR 5825Partially supported by CNR, G.N.F.M. and MURST     

工科大学物理试题库(第4版)

正本题库是使用广、评价高的一款物理试题库,很多高校用它进行教学质量监测,在相关课程的教学中起着重要的作用。本试题库系统可按照使用者的要求生成进行课程评估和平时检查教学效果使用的物理试卷;并可对考试结果进行统计分析;实现对物理课程教学进行科学的评估,提高教学质量,推动物理课程的教学改革。本题库第1版于1987年开始开发,作为由清华大学和其他6所高校合作开发研制的一项科研成果,该成果通过了国家教育主管部门组织的鉴定,鉴定意见建议推广使用。第2版获得国家教育主