低温(CF_3OCO)_2NdCl·6EtOH晶体结构

标题化合物晶体属于空间群P_1,晶胞参数为:a=11.949(6)A,b=12.886(5)A,c=11.557(6)A,α=112.93(3)°,β=115.92(4)°,γ=82.41(4)°。3739个独立衍射数据由四圆单晶衍射仪用低温技术收集。结构用SHELXTL程序重原子法解。结构参数经块矩阵最小二乘法修正后,最终的一致性因子R=0.113。结构分析表明,由氧原子构成钕的八配位稍歪扭的正方反梭柱体,平均Nd-o=2.453A。     

也谈公式Qp=△H的压力条件

本刊1988年第5期发表了“过程热量等于过程焓变的准确压力条件应该是什么”一文(以下简称“条件”一文),作者查阅了78本中外书籍,经分析论证得出的结论是公式Q_P=△H的适用条件为:封闭体系无非体积功的恒压(P_体=常数)过程而不是等压(P_始=P_终=P_外=常数)过程。笔者不同意这种观点。我认为恒压与等压条件的引入是与体积功的计算有关的,若     

Effect of Microstructure of TiO2 Thin Films on Optical Band Gap Energy

TiO2 coatings are prepared on fused silica with conventional electron beam evaporation deposition. After annealed at different temperatures for four hours, the spectra and XRD patterns of TiO2 thin film are obtained. XRD patterns reveal that only anatase phase can be observed in TiO2 coatings regardless of the different annealing temperatures, and with the increasing annealing temperature, the grain size gradually increases. The relationship between the energy gap and microstructure of anatase is determined and discussed. The quantum confinement effect is observed that with the increasing grain size of TiO2 thin film, the band gap energy shifts from 3.4 eV to3.21 eV. Moreover, other possible influence of the TiO2 thin-film microstructure, such as surface roughness and thin film absorption, on band gap energy is also expected.     

Structure and Photoluminescence of Nano-ZnO Films Grown on a Si （100） Substrate by Oxygen- and Argon-Plasma-Assisted Thermal Evaporation of Metallic Zn

Nano-ZnO thin films were prepared by oxygen- and argon-plasma-assisted thermal evaporation of metallic Zn at low temperature, followed by low-temperature annealing at 300℃ to 500℃ in oxygen ambient. X-ray diffraction patterns indicate that the nano-ZnO films have a polycrystalline hexagonal wurtzite structure. Raman scattering spectra demonstrate the existence of interface layers between Zn and ZnO. Upon annealing at 400℃ for i h, the interface mode disappears, and photoluminescence spectra show a very strong ultraviolet emission peak around 381 nm. The temperature-dependent PL spectra indicate that the UV band is due to free-exciton emission.     

Design and Fabrication of 1.06 μm Resonant-Cavity Enhanced Reflective Modulator with GaInAs/GaAs Quantum Wells

A resonant-cavity enhanced reflective optical modulator is designed and fabricated, with three groups of three highly strained InGaAs/GaAs quantum wells in the cavity, for low voltage and high contrast ratio operation. The quantum wells are positioned in antinodes of the optical standing wave. The modulator is grown in a single growth step in an molecular beam epitaxy system, using GaAs/AlAs distributed Bragg reflectors as both the top and bottom mirrors. Results show that the reflection device has a modulation extinction of 3 dB at -4.5 V bias.     

Effect of Alumina and Chromium Interlayers on Microstructures and Optical Properties of Thin Ag Films on Glass Substrates

Effects of alumina and chromium interlayers on the microstructure and optical properties of thin Ag films are investigated by using spectrophotometry, x-ray diffraction and AFM. The characteristics of Ag films in Ag/glass, Ag/l2O3/glass and Ag/Cr/glass stacks are analysed. The results indicate that the insertion of an Al2O3 or Cr layer decreases the grains and influences the reflectance of Ag films. The reflectance of the Ag film can be increased by controlling the thickness of alumina interlayer. The stability of Ag films is improved and the adhesion of Ag films on glass substrates is enhanced by alumina as an interlayer.     

一个误传已久的答案

1错误的答案题目从平面外一点向平面引两条与平面斜交的射线,它们的角为α,这两条射线在平面内的射影的夹角为β,那么α与β之间的关系是( ) (A)α＜β．(B)α＞β．(C)α=β．(D)α≤β．流传的答案是选(A),其实选(A)是错误的,请看以下实例：     

一个误传已久的答案

题目 从平面外一点向平面引两条与平面斜交的射线，它们的角为α，这两条射线在平面内的射影的夹角为β，那么α与β之间的关系是（ ）     

Optical properties and structures of silver thin films deposited by magnetron sputtering with different thicknesses

A series of thin Ag films with different thicknesses grown under identical conditions are analyzed by means of spectrophotometer. From these measurements the values of refractive index and extinction coefficient are calculated. The films are deposited onto BK7 glass substrates by direct current (DC) magnetron sputtering. It is found that the optical properties of the Ag films can be affected by films thickness. Below critical thickness of 17 nm, which is the thickness at which Ag films form continuous films, the optical properties and constants vary significantly with thickness increasing and then tend to a stable value up to about 40 nm. At the same time, X-ray diffraction measurement is carried out to examine the microstructure evolution of Ag films as a function of films thickness. The relation between optical properties and microstructure is discussed.     

窄带干涉滤光片抗击不同输出方式激光的损伤特性研究

利用Nd∶YAG调Q单脉冲激光和自由脉冲激光对硬膜窄带干涉滤光片进行激光损伤阈值的测试，并且采用表面热透镜技术测量了滤光片的吸收率。实验发现:窄带干涉滤光片的吸收率和激光损伤阈值强烈依赖于辐照激光波长与窄带干涉滤光片通带的相对位置；在调Q单脉冲激光作用下，不同中心波长的滤光片损伤形貌存在明显的差别，而在自由脉冲激光作用下，各滤光片的损伤形貌则趋于相同，均表现为典型的热熔烧蚀破坏。根据实验结果，结合损伤形貌，通过驻波场理论对激光作用下滤光片内电场分布的分析与模拟，探讨了两种激光模式作用下滤光片的损伤特征和损伤机理的不同特点。