Advances in liquid crystalline conjugated polymers

We review advances in liquid crystalline (LC) conjugated polymers by focusing on (i) ferroelectric and (ii) photoresponsive LC conjugated polymers. In Part 1, LC polyphenylene derivatives were synthesized through substitution of fluorine‐containing chiral LC groups into side chains. Poly(para‐phenylene) [ P1 ] and poly(meta‐phenylene) [ P2 ] derivatives showed chiral smectic C phases responsible for ferroelectricity. They exhibited quick response to electric field, giving switching times of <1 s between two bistable states. The spontaneous polarization (P_S) of P2 remained unchanged even after the electric field became zero, affording the residual polarization (P_R) whose value was the same as that of P_S. This indicates that P2 has a potential memory function based on FLC nature. In Part 2, poly(para‐phenylenevinylene) [ P5 ] and poly(bithienylene‐phenylene) [ P6 ] derivatives were synthesized by introducing dithienylethene moieties into side chains. Drastic quenching of fluorescence occurred when the photoresponsive moiety changed from an open form to a closed one upon an irradiation of ultraviolet light. The quenched fluorescence was recovered through a photoisomerization from the closed form to the open one. Macroscopically aligned P6 film exhibited a linearly polarized fluorescence with significant anisotropy. Reversible quenching and emitting behavior in anisotropic fluorescence was controlled by the photochemical switching. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2463–2485, 2009     

Orientation Dependent FT Raman Microspectroscopy on Hemp Fibers

Summary: FT Raman microspectroscopy was used for polarization experiments on strained hemp fibre cells. The cellulosic plant fibers were macerated with alkaline and enzymatic solutions. Those cleaned and refined single fiber cells were subjected to micro tensile tests as well as to polarization measurements under the FT Raman microscope. Mechanical parameters of the fiber cells (e.g. E-modulus) were determined and changes in orientation of the  (C O C) structure units of the cellulose were considered with respect to fiber stress and molecular fiber structures. Intensity ratios R₁ and R₂ calculated on the polarized micro FT Raman spectra of the strained fibers describe the order parameter 〈P₂〉 and 〈P₄〉 allowing the quantitative determination of the orientation of the structure units  (C O C) of fiber cellulose with respect to the fiber cell axis.     

Spin-polarized current generated by magneto-electrical gating

We theoretically study spin-polarized current through a single electron tunneling transistor (SETT), in which a quantum dot (QD) is coupled to non-magnetic source and drain electrodes via tunnel junctions, and gated by a ferromagnetic (FM) electrode. The I–V characteristics of the device are investigated for both spin and charge currents, based on the non-equilibrium Green's function formalism. The FM electrode generates a magnetic field, which causes a Zeeman spin-splitting of the energy levels in the QD. By tuning the size of the Zeeman splitting and the source–drain bias, a fully spin-polarized current is generated. Additionally, by modulating the electrical gate bias, one can effect a complete switch of the polarization of the tunneling current from spin-up to spin-down current, or vice versa.     

水热法白宝石晶体和籽晶界面研究

用分光光度计研究发现水热法白宝石晶体和籽晶界面使晶体透过率降低,用大视场偏光显微镜和原子力显微镜分析了该界面的包裹物分布以及界面的显微结构.结果表明平行于(1123)面的籽晶和生长层晶体界面包裹物含量少.界面的缺陷主要来自于晶格畸变及生长初期的温场不稳定所引起的结构缺陷,这也是引起晶体透过率下降的主要因素.     

Inversion of an Atomic Wave Packet in a Circularly Polarized Electromagnetic Wave

We study behavior of an atomic wave packet in a circularly polarized electromagnetic wave,and particularly calculate the atomic inversion of the wave packet.A general method of calculation is presented.The results are interesting.For example,if the wave packet is very narrow or /and the interaction is very strong,no matter the atom is initially in its ground state or excited state,the atomic inversion approaches zero as time approaches infinity.If the atom is initially in its ground state and excited state with the probability 1/2 respectively,and if the momentum density is an even function,then the atomic inversion equals zero at any time.     

光的偏振特性在机动车安全驾驶中的应用

根据光的偏振特性,利用偏振片制作机动车前大灯和偏振片眼镜,实践证明,可以提高机动车夜间行车的安全性.     

偏振光激发的Sr原子电偶极辐射

原子与激光场相互作用产生的自发辐射可以用经典电偶极辐射理论很好的描述.通过改变与Sr原子束相互作用激光的偏振方向,分析探测Sr原子束荧光强度的变化,测定了在远场区的电偶极辐射特性.Sr原子电偶极子在远场区辐射能量的空间方向分布满足sin2θ关系,利用这一规律可以有效地探测到最强的荧光光谱.     

A [Cyclentetrakis(methylene)]tetrakis[2‐hydroxybenzamide] Ligand That Complexes and Sensitizes Lanthanide(III) Ions

The synthesis of the cyclen derivative H₄ L ¹ ?2 HBr containing four 2‐hydroxybenzamide groups is described. The spectroscopic properties of the Ln^III conplexes of L ¹ (Ln=Gd, Tb, Yb, and Eu) reveal changes of the UV/VIS‐absorption, circular‐dichroism‐absorption, luminescence, and circularly polarized luminescence spectra. It is shown that at least two metal‐complex species are present in solution, whose relative amounts are pH dependent. At pH>8.0, an intense long‐lived emission is observed (for [Tb L ¹ ] and [Yb L ¹ ]), while at pH<8.0, a weaker, shorter‐lived species predominates. Unconventional Ln^III emitters (Pr, Nd, Sm, Dy, and Tm) were sensitized in basic solution, both in the VIS and in the near‐IR, to measure the emission of these ions.     

光学元件亚表面缺陷偏振双向反射分布函数

 利用琼斯散射矩阵,借助右手正交基组来表示入射场和散射场,推导出光学元件亚表面缺陷或微粒在不同偏振状态下的双向反射分布函数的表达式。给出了亚表面缺陷在不同入射角条件下,不同偏振状态下的双向反射分布函数与散射方位角之间的关系,以及不同入射角下p偏振入射产生的p偏振双向反射分布函数的3维散射图。结果表明:p偏振入射产生的p偏振双向反射分布函数强烈依赖于入射角、散射角和方位角,且随着入射角的增加,其最小值点所对应的方位角逐渐减小。     

L波段高功率线极化径向线阵列天线理论分析与数值模拟

 探索了L波段的高功率线极化径向线阵列天线。基于三角形栅格形式实现了径向线圆形平面阵列天线,分析并给出了径向线并联馈电网络,并以同轴馈电的水平单圆环线极化天线为基础,利用径向线并联馈电网络设计出了间距小于一个波长下L波段高功率线极化径向线阵列天线。研究结果表明：这种结构实现径向线阵列天线的线极化辐射是可行的,该天线在中心频率1.57 GHz下,增益为19.97 dBi,轴比为-52.06 dB,反射系数为0.105 2;在1.37～1.77 GHz的频率范围内增益大于18.64 dBi,轴向轴比值小于-46.45 dB。