X光底片在位相对标定

本文描述了X光底片在位相对标定技术。其原理是使X射线谱经阶梯形吸收滤片透射后,对X光底片曝光,测量底片的曝光量。文中给出了标定方法和数据处理方法,而且也给出了在X光激光实验中得到的Kodak AA5底片的特性曲线。     

在CPM非稳腔Nd:YAG激光器中用被—被动锁模方法选单脉冲的探讨

在CPM Nd:YAG非稳腔激光器中,我们使用透过率较大的可饱和吸收体使单脉冲序列中的脉冲个数减少到3—5个,在输出的单序列中再使用非线性介质进行处理,可以得到比较接近的单脉冲输出。     

Buckling of laminated plates - A simple finite element based on higher-order theory

A four-noded rectangular element with seven degrees of freedom at each node is developed for buckling analysis of laminated plate structures having any number of layers with a constant thickness of individual layers. The displacement model is so chosen that it can explain adequately the parabolic distribution of transverse shear stresses and the non-linearity of in-plane displacements across the thickness. A geometrical stiffness matrix is developed using in-plane stresses. A wide range of plates from thick to thin are examined under uniaxial loading conditions. The results are compared with the existing analytical and numerical solutions. The present formulations confirm its applicability for buckling analysis of a wide range of plates.     

Laser vaporization: A versatile method for studying metal clusters

Vaporizing solid samples of metals and semiconductors with a YAG Laser is a method well suited for producing molecules and clusters of those materials. The clusters are examined by either laser-induced fluorescence (LIF) or mass spectroscopic methods. The technique is valuable for both gas phase and matrix studies. The method is described and some applications, studying either the structure of small metal molecules or their reactions, are reviewed, with emphasis on our recent results from the LIF studies of LiBe, Al₂ and the reaction of Al with oxygen, yielding A1₂O. For larger clusters, Ion Cyclotron Resonance is an extremely valuable method, as we demonstrate by its application to the reactions of small charged silicon clusters with strong oxidising agents.     

Differential determination of arsenic(III) and total arsenic using flow injection on-line separation and preconcentration for graphite furnace atomic absorption spectrometry

Arsenic(III) can be quantitatively extracted using sodium diethyldithiocarbamate (NaDDTC) as the complexing agent and C18 reversed phase packing as the column material for solid phase extraction. Arsenic(V) must be reduced to its trivalent oxidation state prior to extraction. A mixture of sodium sulphite, hydrochloric acid, sodium thiosulphate and potassium iodide was found to be optimum for on-line reduction. When the sorbent extraction is carried out without and with the addition of the reduction mixture, arsenic(III) and total arsenic can be determined sequentially by graphite furnace atomic absorption spectrometry with detection limits (3 σ) of 0.32 ng for As(III) and 0.43 ng for total arsenic. A 7.6-fold enhancement in peak area compared to direct injection of 40 μl samples was obtained after 60 s preconcentration. Results obtained for sea water standard reference materials, using aqueous standards for calibration, agree well with certified values. A precision of 5.5% RSD was obtained for total arsenic in a sea water sample (1.65 As). Results obtained for synthetic mixtures of trivalent and pentavalent arsenic agreed well with expected values.     

用于二聚物三能级蒸气激光系统的环形谐振腔设计

针对二聚物三能级蒸气激光系统增益相对于泵浦光方向显著的不对称特性,本文设计了一种稳定的能够充分利用介质增益特性的环形谐振腔,给出了象散和慧差补偿及泵浦激光与谐振腔匹配的条件。文中还给出了Na_2B~1Ⅱ_u-X~1∑_g~+跃迁激光谐振腔设计数据。     

0.351μm激光辐照Au盘靶吸收、散射规律的实验研究

在“星光Ⅱ”激光装置上，利用80只分立式探测器研究了约0.8ns，0.351μm激光辐照Au盘靶的吸收、散射．结果表明，强度约为5×10¹⁴W/cm²的激光以10°角入射，吸收可达90%以上；但是，以45°角入射，吸收仅为75%左右，散射高达25%．散射主要来自未被等离子体充分吸收的激光在弯曲临界面上的反射，同时伴随少量受激布里渊散射．吸收的理论计算与实验结果进行了比较，两者符合较好． 关键词：     

Dynamic NMR study of the flexibility of 2-amino-3-aroyl-4,6-diaryl-pyrylium salts

Dynamic NMR investigations of a number of 2-amino-3-aroyl-4,6-diaryl-pyrylium salts were carried out. The barrier to rotation of the partial C, N double bond was determined and proved to be in the range of 62 to 63 kJ/mol. Quantum chemical calculations of bond orders and electron densities of the different atoms in the molecules show the distinct double bond character of the exocyclic C, N bond. This is in agreement with the relatively high barrier to rotation. By quantum chemical ab initio 3-21G calculations, the dynamic behaviour of this kind of compounds was simulated; two pairs (image and mirror image) of ground state conformations, in coincidence with the experiment, were obtained. Received: 10 May 1996 / Revised: 1 July 1996 / Accepted: 4 July 1996     

Fluorides of ruthenium and chromium: Theoretical studies

The electronic and structural characteristics of CrF₅, CrF₄, RuF₅ and RuF₄ were studied. Ab initio (SCF-CI) calculations were performed with different structures and spin states for each complex. The favored conformation always corresponds to the highest multiplicity: doublet for CrF₅ in D_3h, triplet for CrF₄ in T_d, quadruplet for RuF₅ in C_4v and quintuplet for RuF₄ in D_4h symmetry.     

一种新的奇偶非线性相干态及其量子统计性质

定义了一种新的奇偶非线性相干态即算符B2[B=af(N)]的两个正交归一本征态,利用数值计算方法研究了它们的量子统计性质.结果表明,与通常的奇偶相干态不同,在参数|β|变化的某些范围内,只有偶非线性相干态可以存在压缩效应,而振幅平方压缩和反聚束效应在这两个态中均可以呈现 关键词： 新的奇偶非线性相干态 压缩 振幅平方压缩 反聚束效应