Microscopic fluorescence imaging of bulk defect clusters in KH(2)PO(4) crystals

A microscopic fluorescence imaging system is used to detect optically active centers located inside a transparent dielectric crystal. Defect centers in the bulk of KH(2)PO(4) crystals are imaged based on their near-infrared emission following photoexcitation. The spatial resolution of the system is 1mum in the image plane and 25mum in depth. The experimental results indicate the presence of a large number of optically active defect clusters in different KH(2)PO(4) crystals, whereas the concentration of these clusters depends on the crystal sector and growth method.     

Simultaneous spatial and temporal walk-off compensation in frequency-doubling femtosecond pulses in beta-BaB(2)O(4)

We experimentally demonstrate the benefits of simultaneous compensation of spatial and temporal walk-off in frequency doubling of 800-nm 250-fs pulses, using three active and two compensating beta-BaB(2)O(4) crystals. The compensating crystals reverse both birefringent and group-velocity walk-off, resulting in a factor-of-4.5 improvement in doubling efficiency relative to one of the active crystals while maintaining the short pulse duration and the symmetric spatial profile that are characteristic of the single crystal.     

Critical layer thickness of GaIn(N)As(Sb) QWs on GaAs and InP substrates for (001) and (111) orientations

The aim of this work is to examine the effect of dilute nitride and/or antimonite on the critical layer thickness of GaInAs quantum wells on GaAs and InP substrates by means of Matthews and Blakeslee force model. The study provides a comparison of the critical layer thickness of the related GaIn(N)As(Sb) QWs in (001) and (111) orientation. Our calculations indicate the importance of antimonite and the proper usage of it with dilute nitrides in order to tailor the active layer thickness and emission wavelength of quantum well laser devices.     

High-Resolution Spectroscopy and Analysis of the nu(3) and nu(4) Fundamentals of Monoisotopic (70)GeF(4)

The first high-resolution study on germanium tetrafluoride is reported. We used a monoisotopic sample of (70)GeF(4). The FTIR spectra of the two infrared active fundamentals, namely the nu(4) (bending) and nu(3) (stretching) modes, were recorded at a temperature of ca. 210 K and a resolution (1/maximum optical path difference) of 0.0031 and 0.0023 cm(-1), respectively. These spectra were analyzed using the STDS software developed in Dijon. In both cases, we obtained a fit with a root mean square better than 1x10(-3) cm(-1). Both bands show very regular structures with no detectable perturbation. Copyright 2001 Academic Press.     

氧原子在Zr(0001)表面附近的扩散

在密度泛函理论计算的基础上,利用微动弹性带（nudged elastic band）方法研究了氧原子在Zr（0001）表面附近的扩散.首先计算了氧原子从稳定的表面面心立方（SFCC）位置向表面六角密排位置的扩散激活能（0.77 eV）;然后计算了氧原子从稳定的SFCC位置扩散到表面下第1层与第2层之间的八面体间隙位置,再继续向表面下第2层与第3层之间的八面体间隙位置扩散的激活能,在此过程中氧原子需克服两个能垒,其激活能分别为2.14和2.57 eV.结果表明,氧原子在Zr（0001）表面上方的扩散比较容易,而氧原子向Zr（0001）表面下的扩散相对较难. 关键词： Zr（0001）表面 微动弹性带 氧的扩散     

Electroluminescent properties of dimeric bis(2-(2′-hydroxyl phenyl)benzthiazolate)zinc (II) complex

A blue shifted photoluminescent emission in bis(2-(2′-hydroxyl phenyl)benzthiazolate)zinc (II) complex, ZBZT, arises out of the dimeric structure, typical of the localized electron density around the non-bridged ligand in the excited state of the complex. An average decay lifetime of 4.8 and 3.0 ns for the ligand and the complex, respectively indicates an energy transfer from the ligand to the metal. A PL quantum efficiency of about ?_ZBZT=0.45 in DMF solution is observed, in comparison to the Alq₃, complex, ?_Alq3=0.116. Semi empirical ZINDO/S-SCF-CI calculations support the dominance of non-bridged ligand moiety in controlling the photoluminescent properties. An unusually broad white light (FWHM ∼220 nm) electroluminescent emission in the two layer device structure brings out the features of an exciplex formation between the active layer ZBZT/TPD interface, which is studied at different current densities. Such a broadened emission is verified for different thicknesses of the active layer substantiating the role of exciplex formation.     

Photon conversion in Bi(3+)/Pr(3+)-codoped CaTiO(3)

The luminescence properties of CaTiO(3) both singly and doubly doped with Bi(3+) and Pr(3+) have been measured in different experimental conditions in order to investigate the de-excitation processes active in these materials and in particular to understand the mechanism responsible for the significant increment of the red emission observed in the codoped system upon near-ultraviolet (NUV) excitation. The steady state spectra and the decay profiles have been analyzed in the light of the possible interactions between active ions and host lattice. The general model applied to the analysis of the temporal profiles of the emission allows us to assess which are the main mechanisms involved in the Bi(3+) → Pr(3+) sensitization process.     

High-power self-mode-locked Yb:Y(2)O(3) ceramic laser

We have experimentally demonstrated a high-power self-mode-locked Yb:Y(2)O(3) ceramic laser. Without any additional active or passive element in the cavity, self-started cw mode-locking was achieved. The maximum output power was as high as 2.7 W with a pulse duration of 1.1 ps. Numerical studies show that the diffraction loss induced by thermal lens aberration, in combination with the Kerr self-focusing effect in the gain medium, results in the mode locking of the laser. To our knowledge, this is the first self-mode-locked ceramic laser.     

Talbot holographic illumination nonscanning (THIN) fluorescence microscopy

Optical sectioning techniques offer the ability to acquire three‐dimensional information from various organ tissues by discriminating between the desired in‐focus and out‐of‐focus (background) signals. Alternative techniques to confocal, such as active structured illumination, exist for fast optically sectioned images, but they require individual axial planes to be imaged consecutively. In this article, an imaging technique (THIN), by utilizing active Talbot illumination in 3D and multiplexed holographic Bragg filters for depth discrimination, is demonstrated for imaging in vivo 3D biopsy without mechanical or optical axial scanning.     

5-冰片氧基-3,4-二取代-2(5H)-呋喃酮NMR研究

总结了一系列光学纯5-冰片氧基-3,4-二取代-2(5H)-呋喃酮的¹H NMR和¹³C NMR化学位移数据,研究了不同取代基对结构及化学位移的影响.     

Magnetic couplings in CsV(2)O(5): a new picture

Concerning its magnetic properties, the layered vanadate CsV(2)O(5) has long been considered as formed by isolated spin-1/2 dimers characterized by a large antiferromagnetic coupling of about 146 K. This interpretation was supported by both magnetic susceptibility measurements and the obvious presence of magnetically active strongly dimerized V(4+) ions. In this work we investigate the magnetic properties of this compound through an extensive use of the broken-symmetry formalism in the framework of density-functional theory. Our calculations demonstrate that the system is built from strongly dimerized alternating chains where the structural and magnetic dimers are distinct from each other.     

新试剂1-（偶氮苯基）-3-（4,5-二甲氧基-2-苯甲酸）-三氮烯与铜（Ⅱ）的显色反应

研究了1-（偶氮苯基）-3-（4,5-二甲氧基-2-苯甲酸）-三氮烯（ABDMBAT）试剂与Cu（Ⅱ）的显色反应。在TritonX-100的存在下,pH 11.0的Na2B4O7-NaOH缓冲溶液中,该试剂与铜形成红色络合物,ABDMBAT与Cu（Ⅱ）形成的络合物的最大吸收峰位于540nm处,表观摩尔吸光系数ε=8.26×104L.mol-1.cm-1,Cu（Ⅱ）在0—14μg/25mL范围内服从比耳定律。     

Passively synchronized erbium (1550-nm) and ytterbium (1040-nm) mode-locked fiber lasers sharing a cavity

Erbium and ytterbium fiber lasers were firmly synchronized by nonlinear interaction in active media placed in the same cavity. A two-color femtosecond-picosecond pulse train at largely separate wavelengths of 1.55 and 1.04 microm was generated. Optimizing the laser cavity to enhance the cross-phase modulation in the gain materials has yielded a large mismatch of 20 microm between the two laser cavities.     

A megawatt excimer laser of small discharge volume (3.8 cm3)

We demonstrated intense laser action form a 14 cm gain length, 3.8 cm³ active volume XeCl laser. The laser peak power of 1.3 MW was comparable with the best results obtained from a similar small active volume excimer laser, and the laser energy of 40 mJ per pulse obtained from our device was considerably higher.     

Measurement of the rate of nu(e) + d --> p + p + e(-) interactions produced by (8)B solar neutrinos at the Sudbury Neutrino Observatory

Solar neutrinos from (8)B decay have been detected at the Sudbury Neutrino Observatory via the charged current (CC) reaction on deuterium and the elastic scattering (ES) of electrons. The flux of nu(e)'s is measured by the CC reaction rate to be straight phi(CC)(nu(e)) = 1.75 +/- 0.07(stat)(+0.12)(-0.11)(syst) +/- 0.05(theor) x 10(6) cm(-2) s(-1). Comparison of straight phi(CC)(nu(e)) to the Super-Kamiokande Collaboration's precision value of the flux inferred from the ES reaction yields a 3.3 sigma difference, assuming the systematic uncertainties are normally distributed, providing evidence of an active non- nu(e) component in the solar flux. The total flux of active 8B neutrinos is determined to be 5.44+/-0.99 x 10(6) cm(-2) s(-1).     

Epoxy bond and stop-etch (EBASE) technique enabling backside processing of (Al)GaAs heterostructures

The epoxy bond and stop-etch (EBASE) technique enables both the frontside and the backside processing of very thin (3000Å) GaAs/AlGaAs epitaxial layer structures. Using this technique, a conventionally processed epitaxial layer structure is inverted and epoxied to a new host substrate. The original substrate is removed leaving only the original epitaxial structure expoxied to the host substrate. The exposed backside of the epitaxial structure may then be processed. Because the structures fabricated using this technique are so thin, mesas, Schottky gates, and ohmic contacts may be defined in close proximity both above and below the active device layers.     

负膨胀材料Zn(CN)_2和Cd(CN)_2的晶格振动分析

运用群论理论对负膨胀系数材料Zn(CN)2和Cd(CN)2的晶格振动进行了对称性分类,利用第一性原理密度泛函理论计算了它们布里渊区中心点的声子频率和Grüneisen参数,根据计算得到的各个模式所对应的本征矢对各个振动模式进行了指认,根据各模式Grüneisen参数讨论了负膨胀机理。在11个光学振动模式中,一个属于Zn/Cd原子的晶格振动模,位于223 cm-1/154 cm-1;5个属于C≡N刚性单元平移振动模;3个属于C≡N刚性单元天平动;2个属于C≡N刚性单元内振动。有7个振动模为拉曼活性,4个振动模为红外活性,两个振动模红外和拉曼均为非活性。C≡N刚性单元的3个低频平移振动模和全部天平动模的Grüneisen参数为负,对负热膨胀的产生有贡献,振动频率为47 cm-1的平移振动模具有最大的负Grüneisen参数,对负膨胀贡献最大。     

The nu(2), nu(4) + nu(5), nu(6) + nu(9), and nu(8) Band System in 1,1,1-Trifluoroethane

High-resolution FTIR spectra of 1,1,1-trifluoroethane (HFC-143a) have been recorded in the region from 1370 to 1470 cm(-1) with an unapodized resolution of 0.0016 cm(-1) at room temperature and of 0.004 cm(-1) at 183 and 100 K. The two main infrared active bands of A(1) symmetry have been shown to be nu(2) at 1407.5 cm(-1) and nu(4) + nu(5) at 1440.5 cm(-1). With the aid of Raman spectra, the two infrared inactive bands of E symmetry in this spectra region have been shown to be nu(8) at 1457.5 cm(-1) and nu(6) + nu(9) at 1446.2 cm(-1). The nu(2) band was analyzed as an isolated band, whereas the nu(4) + nu(5) band was analyzed as part of the triad nu(4) + nu(5), nu(6) + nu(9), and nu(8). Copyright 2000 Academic Press.     

(002)取向AIN薄膜的Raman光谱

（００２）取向ＡＩＮ薄膜的Ｒａｍａｎ光谱赵永年王波何志罗微邹广田（吉林大学超硬材料国家重点实验室长春１３００２３）ＲａｍａｎＳｐｅｃｔｒａｏｆＡＩＮＦｉｌｍｓＯｒｉｅｎｔｅｄｉｎ（００２）ＺｈａｏＹｏｎｇｎｉａｎ，ＷａｎｇＢｏ，ＨｅＺｈｉ，ＬｕｏＷｅ...     

Treatment of Low and Medium Active Waste by Hexacyanocobaltate(III)

The commercially available CO₃[Co(CN)₆]₂·12H₂O was used in this study as inorganic ion exchanger. The uptake of caesium and cobalt from simulated borate reactor waste on the exchanger was conducted as a function of pH and concentration of caesium or cobalt in solutions. The same study was also carried out on the sorption of caesium from simulated medium active waste. In addition some experiments were carried out on the sorption of radionuclides present in a real medium active waste concentrate.