The ground state rotational spectrum of SO2F2

The analysis of the ground state rotational spectrum of SO₂F₂ [K. Sarka, J. Demaison, L. Margulès, I. Merke, N. Heineking, H. Bürger, H. Ruland, J. Mol. Spectrosc. 200 (2000) 55] has been performed with the Watson’s Hamiltonian up to sextic terms but shows some limits due to the A and S reductions. Since SO₂F₂ is a quasi-spherical top, it can also be regarded as derived from an hypothetical XY₄ molecule. Thus we have developed a new tensorial formalism in the O(3)⊃T_d⊃C_2v group chain (M. Rotger, V. Boudon, M. Loëte, J. Mol. Spectrosc. 216 (2002) 297]. We test it on the ground state of this molecule using the same experimental data (10 GHz-1 THz region, J up to 99). Both fits are comparable even if the formalisms are slightly different. This paper intends to establish a link between the classical approach and the tensorial formalism. In particular, our tensorial parameters at a given order of the development are related to the usual ones. Programs for spectrum simulation and fit using these methods are named C_2vTDS. They are freely available at the URL:http://www.u-bourgogne.fr/LPUB/c2vTDS.html.     

Investigation of the three-dimensional microstructure of Cu-Sn(Pb) diffusion zones by means of ion beam sputtering, scanning electron microscopy and lattice source interferences

On model substances of Cu-Sn(Pb) solders it is shown by the combined use of several physical analytical methods that the intermetallic compounds formed during the annealing process have a crystalline structure, which can be observed also three-dimensionally by ion etching. Moreover, grain boundaries as well as phases become visible, and it is possible to determine the crystallographic orientation of the individual crystals in the Cu starting material and in the diffusion zones by means of the Kossel technique. As a result of the investigations, conclusions can be drawn with respect to the diffusion process, especially also to the crystallographic structure of the diffusion zones and the dendritic growth.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

Preparation and Sensitivity of SnO2 Grafted MCM-41 Sensor

Tin dioxide is one of the most widely used semiconductor gas sensor to detect reducing gases1-3. The sensing mechanism of SnO2 is usually based on the change of the resistance of the sensor in different gas environment. In air, the surface-adsorbed oxygen species on the surface of SnO2 act as surface acceptors of electrons, hence diminishing the conductivity of SnO2. However, when reducing gases such as H2, CO, or CH4 are introduced in the air stream, the resistance of the SnO2 sensor is …     

Probabilistic properties of neuron spiking time-series obtained in vivo

Probabilistic properties of spiking time-series obtained in vivo from singular neurons belonging to Red Nucleus of brain are analyzed for two groups of rats: genetically defined rat model of depression (Flinders Sensitive Rat Line - FSL) and a control (healthy) group. The FSL group shows a distribution of interspike intervals with a much longer tail than that found for normal rats. The former distribution (for the FSL group) indicates a power-law with exponent α = - 1±0.1. A simple thermodynamic (noise) model is elaborated to explain obtained results. Received 13 May 2001 and Received in final form 20 September 2001     

Photoluminescence of SrGa2S4:Sn,Re(=Ce, Gd) phosphors

The photoluminescence (PL) spectra, PL excitation spectra, color coordinates, and X-ray diffraction spectra are reported for SrGa₂S₄:Sn,Re(=Ce and Gd, respectively) phosphors. By mixing SrGa₂S₄:Sn,Ce phosphors with different Ce³⁺ concentrations, white emissions can be obtained under the excitation of a 340-nm UV LED. Emissions in the green to yellow color range can be obtained from SrGa₂S₄:Sn,Gd phosphors. The rare earth ions enhance the green emission band, which peaks at 534 nm, instead of the yellow one. The origin of this enhancement is discussed. The resonant energy transfer rates are estimated in the cases from Ce³⁺ to the green and yellow centers of Sn²⁺ and between the yellow centers and the green centers.     

Ln2Sn2O7：Er3+纳米晶的制备及发光性能研究

采用溶胶-凝胶法合成Ln₂Sn₂O₇:Er³⁺(Ln=La,Gd,Y)纳米晶。通过X射线衍射和场发射扫描电子显微镜测试了样品的晶体结构和形貌,同时对样品的上转换发光性能进行了测试。结果表明:在980 nm连续激发光的激发下,样品主要表现为绿光发射。发射中心在528,549 nm的绿光和672 nm处的红光发射分别对应Er³⁺离子的⁴S_3/2→⁴I_15/2、²H_11/2→⁴I_15/2和 ⁴F_9/2→⁴I_15/2跃迁。以La₂Sn₂O₇:Er³⁺纳米晶为例,Er³⁺离子的摩尔分数为7%、退火温度为1 150℃是其制备的最佳条件,此时其各个发射峰的强度最高。对La₂Sn₂O₇:Er³⁺的发光强度与激发功率关系的研究表明,其绿光和红光发射均为双光子过程。激发光吸收和能量转移是La₂Sn₂O₇:Er³⁺纳米晶上转换发光的主要机制。     

2,6-双(三甲基锡)-4,8-双(2-乙基己氧基)苯并[1,2-b∶4,5-b']二噻吩的合成与多核NMR研究

以苯并[1,2-b∶4,5-b´]二噻吩-4,8-二酮为原料合成了一种聚合物太阳能电池材料的单体2,6-双(三甲基锡)-4,8-双(2-乙基己氧基)苯并[1,2-b∶4,5-b´]二噻吩. 通过多核1D和2D NMR技术（包括1D ¹H、¹³C、¹¹⁹Sn、¹¹⁷Sn NMR、DEPT、选择性1D TOCSY及2D¹H-¹H COSY、gHSQC、gHMBC）表征了目标分子结构,完成了 ¹H、¹³C、¹¹⁹Sn 与¹¹⁷Sn NMR化学位移归属,并探讨了该化合物的NMR谱线特征.     

New Transition Metal Oxo‐Thiostannate: Synthesis,Characterization, and Investigation of its Photocatalytic Properties

The new transition metal oxo‐thiostannate {[Ni(cyclen)]₆[Sn₆S₁₂O₂(OH)₆]} · 2(ClO₄) · 19H₂O ( 1 ) was prepared under hydrothermal conditions using Na₄SnS₄ · 14H₂O and [Ni(cyclen)](ClO₄)₂ as reactants. In the crystal structure the rare [Sn₆S₁₂O₂(OH)₆]^10– anion is observed, which is composed of SnS₂O(OH)₃ and SnS₄O₂ octahedra, and SnS₄ tetrahedra sharing edges and corners. The anion is expanded by six Ni²⁺ centered complexes via Ni–S and Ni–OH bonds. The photocatalytic properties for the visible light driven hydrogen evolution reaction shows that 26.6 mmol · g^–1 H₂ were evolved after 3 h.     

锡负载量对PtSn/Al2O3催化丙烷脱氢性能的影响

采用羰基合成-浸渍法制备了不同Pt/Sn摩尔比(3:1, 1:1, 1:2和1:3)的PtSn/Al₂O₃催化剂, 利用N₂吸附-脱附实验、 X射线衍射(XRD)、 透射电子显微镜(TEM)、 吡啶吸附红外光谱(Py-IR)和热重-差热分析(TG-DTA)等手段对其进行了表征, 研究了Sn负载量对PtSn/Al₂O₃的结构性质及催化丙烷脱氢性能的影响. 结果表明, 制备的PtSn/Al₂O₃具有较高的丙烯选择性和稳定性. 当Pt/Sn摩尔比为3:1和1:1时, 铂和锡在催化剂上主要以Pt₃Sn和PtSn合金形式存在, 合金的形成明显改善了催化剂的脱氢性能, 可抑制金属颗粒的高温烧结; 当Pt/Sn摩尔比为1:2和1:3时, 铂主要以金属形式存在. 随着Sn负载量的增加, 催化剂上L酸性位逐渐减少, 丙烷转化率降低, 丙烯选择性增加, 同时促使反应积炭从金属表面向载体迁移, 改善了催化剂的稳定性.     

阿达玛变换在激光告警技术中的应用

系统信噪比一直是制约激光探测武器性能的关键性因素之一。为提高系统探测信噪比,利用阿达玛变换方法,在计算模板大小（17.48×17.48mm）和码元数N=255的基础上,详细介绍了Sn循环矩阵的生成,最后选择液晶空间光调制器充当编码模板。通过在液晶面板上不同位置施加不同的电压,利用旋光效应对通过的激光衍射条纹进行控制,按其通过与否（1/0）进行编码。在这一方法指导下进行了系统的仿真实验研究并获得成功。实验结果表明：将阿达玛变换应用于激光光谱测量,在不增加测量次数的情况下,可以有效地提高系统的信噪比。