STRUCTURES OF Si AND Ge CLUSTERS UNDER MODIFIED STILLINGER-WEBER POTENTIAL

Structural behaviors of silicon and germanium clusters under the recently proposed modified Stillinger-Weber (SW) potential have been studied by molecular dynamics method along with the con-jugate-gradient optimization. Since the SW potentials have been derived from the properties of bulk materials, it gives relatively large discrepancy when the cluster number is small, e.g. n=3 and 4. When n>4, the ground-state structures under the modified SW potential are close to that from the first-principle calculation. The binding energies are also improved under the modified SW potential. These results may be attributed to the relative enhancement of the two-body term over the three-body term in the modified SW potential, which leads to structures with a preferential coordination number 4. Structural behaviors of germanium clusters are similar to those of silicon.     

MEASUREMENT OF ANISOTROPIC ACTIVATION ENERGIES IN HIGH-Tc SUPERCONDUCTORS

For single crystalline and melt-textured samples there exist several different activation energies for fluxoid creep, which are related to various vortex orientations and hopping directions. We discuss how to obtain these anisotropic activation energies from magnetic relaxation data and present measured results of a melt-textured YBCO sample.     

ELLIPSOMETRIC SPECTRA OF CONDUCTING POLYANILINE

We report the ellipsometric spectrum studies on a new kind of conducting polymers, polyaniline. In the UV-visible range (1.4-4.8eV photon energy region) the absorption coef-ficient, the complex dielectric function and the refractive index of polyaniline as functions of photon energy are obtained. The spectra of nonconducting and fully conducting polyaniline have been analyzed and discussed. The experimental results show that the emeraldine base form of polyaniline has a large energy gap (E_g～3.6eV) and its absorption spectrum shows a broad exciton absorption peak centered at 2 eV. The absorption spectrum of emeraldine salt after protonation have four absorption peaks centered at 1.5, 1.83, 3.0 and 3.88eV. We also investigated the spectrum evolution of the samples from nonconducting (σ<10^-9Ω^-1·cm^-1) to conducting (σ≈10⁺¹Ω^-1·cm^-1) states, and give the dielectric function and the refractive index of the samples.     

顺磁物质CeF3磁光Faraday效应及其温度特性的量子理论

本文计算了顺磁物质CeF₃因Ce³⁺离子从基态能级4f至5d的电偶极跃迁产生的Fara-day旋转。讨论晶场对Ce⁺³离子4f和5d能级的影响,通过唯象地引入一个与磁化强度M成正比的“附加磁场”H_m=λM,由此获得4f离子在外加磁场和“附加磁场”的共同作用下的一级Zeeman分裂。经劈裂后的两个子能级上各自产生左、右圆偏振光激发的电偶极跃迁,导致磁光Faraday效应。对于波长为0.6328μm的入射光,在60—300 关键词：     

ICP—AES法测定人体胎盘血清中15种微量元素

用ICP-AES法测定了人体胎盘血清中15种微量元素。本法具有灵敏度较高,校正曲线的线性范围宽,基体效应小,尤其是进样量少等优点。本法可同时测定多种元素。     

ICP-AES中基体干扰效应及其机理研究——Ⅰ.基体干扰效应的一般分布规律

本文以Na、ca、Al、Zn作为主要基体元素,在不同ICP发射光谱仪上考察了20多条分析谱线受到的干扰情况,初步总结了基体干扰效应的一般规律。结果表明,在常用分析条件下,一般金属元素具有与易电离元素类似的基体效应,即在较低观察区域对测定谱线信号产生增感,而在正常观察区域产生抑制;从增感转向抑制的零干扰点主要出现在感应圈上方8～14mm的观察区域,这一结果为实际分析条件的优化提供了有益的依据。     

甲酚紫非线性光学性质的研究

报道了甲酚紫染料的非线性光学性质的实验研究方法及其结果.利用简并四波混频技术,测量得到甲酚紫甲醇溶液(浓度为5×10~(-4)M)的三阶非线性极化率X~(3)为2.0×10~(-10)esu.此外,利用不同强度皮秒脉冲相关技术得到了甲酚紫甲醇溶液的吸收恢复时间τ_(21)为163ps.     

喇曼感生克尔效应光谱的琼斯矩阵分析

介绍喇曼感生克尔效应光谱(RIKES)的琼斯(Jones)矩阵分析方法.探测光束的传输强度不仅由所经过的每一个光学器件的琼斯矩阵所决定,而且还受到强的泵波在非线性介质样品中感生依赖于强度的二向色性和双折射(克尔效应)对琼斯矩阵的影响.同时计及样品和光学器件由强泵波作用下感生应力和其他外部产生的线双折射对喇曼感生克尔效应光谱观察的不利影响,导出测量系统的功率传输函数的完整表达式和喇曼感生克尔效应光谱的实现观察条件,最后简述以甲笨(C_7H_8)液体为试样的喇曼感生克尔效应光谱实验结果分析.     

一组新型络合物晶体结构与光学性能的研究

研究了二氯三烯丙基硫脲合镉(ATCC),二氯三烯丙基硫脲合汞(ATMC)和二溴三烯丙基硫脲合镉(ATCB)三种晶体的结构特点.首次报道了ATMC和ATCB晶体的非线性光学系数及倍频性能;文中分析比较了三种晶体的非线性光学性能;讨论了晶体结构与性能的关系,为探索高效非线性光学新材料提供依据.     

铥原子激发能级超精细结构常数的测定

用铥空心阴极灯,采用光电流光谱技术测得铥原子21条一级跃迁谱线,确定了相应跃迁上能级的超精细结构常数,其中7个能级的参数为首次发表,运用同一空心阴极灯,采用双色双光子级联共振技术,由荧光法首次测得4个第二激发能级的超精细结构常数.