Three-Body Phase Shift in One-Dimensional 2 + 1 Scattering

For a model of three particles on a line, subject to attractive delta-function interactions, we consider the phase shift. We do this from the point of view of the calculation of the S-matrix in a hyperspherical adiabatic basis (an adiabatic S-matrix), and for energies ranging from the (negative) energy of the two-body bound state to a total energy of zero. We derive analytical expansions and present numerical work, for different approximations, and compare with the exact results that we obtain from the work of McGuire, whose model we have borrowed. We show that the simplest adiabatic approximation gives results that are qualitatively wrong, but that better approximations yield, for most of our range, excellent agreement with the exact result. Understanding the threshold behaviour, however, requires a zero-energy three-body bound state, or resonance, previously unsuspected for this model. The methods developed for the case of the simplest adiabatic approximation also yield threshold and low-energy results applicable to the two-body problem in two dimensions. Received December 23, 1996; revised May 13, 1997; accepted for publication June 19, 1997     

Formation of small single-layer and nested BN cages under electron irradiation of nanotubes and bulk material

12 N₁₂, B₁₆N₁₆ and B₂₈N₂₈ octahedra which were predicted to be magic clusters for the BN system from electronic structure calculations. Received: 2 March 1998     

Ⅱ—Ⅵ族稀磁半导体Cd1—xMnxTe／Cd1—yMnyTe超晶格的光调制反 …

本文报道用分子束外延技术生长的Ｃｄ１－ｘＭｎｘＴｅ／Ｃｄ１－ｙＭｎｙＴｅ超晶格样品在８０Ｋ下的光调制反射谱实验结果，观测到１１Ｈ，２２Ｈ，３３Ｈ和１１Ｌ等激子跃迁结构。计及晶格失配导致的应力效应，对子能级结构进行了理论计算。     

石墨探针技术／石墨炉原子吸收光谱测定人发中痕量锰

本文采用探针原子化技术对痕量锰进行了一系列条件试验，试验结果表明，石墨探针炉法具有灵敏度高，检出限低，重现性好，简便快速等特点，应用于人发中痕量锰的测定，结果满意。     

香兰素对甲苯胺希夫碱稀土配合物的红外光声光谱

研究了香兰素对甲苯胺希夫碱及其金属配合物在３８００－２００ ｃｍ＾－１范围的傅里叶变换红外光谱光谱，对主要谱带进行了经验归属。     

活血逐瘀颗粒剂中芍药甙的含量测定

本文采用了薄层色谱法将复方制剂活血逐瘀颗粒中的芍药甙与其他成分分离，用紫外分光光度法测定芍药甙的含量，其平均回收率为９８．７４％，变异系数为１．４３％，本文方法抗干扰能力强，适合于中药复方制剂中芍药甙的定量分析。     

Electric-pulse-induced local conducting area and joule heating effect in VO2/Al2O3 films

We investigated the effect of an electric-pulse on the insulator–metal phase transition of VO₂/Al₂O₃ films using synchrotron-based infrared microspectroscopy. By monitoring the time-resolved optical response, we could demonstrate that local conducting areas are formed under the influence of the electric-pulse, and the Joule heat generated from the local current flow drives a consecutive thermal phase transition in the adjacent sample area.     

Low-field magnetoresistance of Ag-substituted perovskite-type manganites

A series of bulk polycrystalline Nd_1−xAg_xMnO₃ samples were prepared by conventional solid-state reaction processing, for x between 0.1 and 0.5. The structure, magnetism, and magnetoresistance (MR) of the samples are investigated. The X-ray diffraction patterns show that the x=0.1 sample is a single perovskite structure, while x0.167, samples consist of a ferromagnetic perovskite phase and two nonmagnetic phases, Ag and Mn₃O₄. The MR of Nd_1−xAg_xMnO₃ is enhanced by increasing the composition of Ag. Compared with the sample of x=0.1, the x=0.5 sample has a significantly larger value of low-field MR. The enhanced low-field MR is related to the spin-dependent scattering of spin-polarized electrons at the interfaces between the perovskite grains and silver granules.     

Analytical expression for the diffraction field of an axicon using the ray-tracing and interference method

We present a simple analytical expression for calculating the vector field distribution behind an axicon using the ray tracing and interference method. This expression can be used for analyzing vector beam propagation throughout the whole space behind the axicon, with any base angle. Using the present analytical expression, we have studied the propagation characteristics of the four kinds of polarizations, linear polarization, left-handed circular polarization (i.e., the radial polarization), right-handed circular polarization, and azimuthal polarization, incident on the axicon. We found that the longitudinally-polarized component has to be considered for a large base angle and high refractive index of axicons, apart from the azimuthally-polarized beam of incidence. PACS 42.15.Dp; 42.60.Jf; 42.25.Hz     

Synthesis of tungsten carbide nanopowder via submerged discharge method

Tungsten carbide nanopowder was prepared via pulsed discharge of bulk tungsten and graphite rods immersed in pure ethanol. The effect of discharge parameters on the characteristics of final products was investigated. Structural and morphological characterization of nanopowder was performed by means of X-ray diffraction analysis and transmission electron microscopy. In order to determine the feasibility of using synthesized material as an electrocatalyst, tungsten carbide nanopowder was tested for hydrogen evolution. A correlation was found between morphology of nanoparticles, their phase composition and electrocatalytic activity.