氢同位素化合物TiH2,TiD2和TiT2的电子振动近似理论方法

根据原子分子反应静力学和群论,确定TiH2,TiD2和TiT2的基电子状态为3A2.应用基函数6-311G**和密度泛函理论B3P86方法,全电子计算了氢同位素分子及其钛化物的能量E、定容热容Cv和熵S.应用电子振动近似理论,即用单个分子TiH2,TiD2和TiT2中的电子和振动能量和熵近似代表他们处于固态时的能量和熵. 计算所得到的金属钛的氢化热力学函数ΔH0,ΔS0,ΔG0以及平衡压力与温度的关系,与文献符合很好,这表明电子振动近似理论的可应用性,选用金属钛作为中子靶是很正确的.     

氢同位素化合物TiH2，TiD2和TiT2的电子

根据原子分子反应静力学和群论，确定TiH2，TiD2和TjT2的基电子状态为^3A2．应用基函数6-311G^＊＊和密度泛函理论B3P86方法，全电子计算了氢同位素分子及其钛化物的能量E、定容热容Cv和熵S应用电子振动近似理论，即用单个分子TiH2，TiD2和TjT2中的电子和振动能量和熵近似代表他们处于固态时的能量和熵,计算所得到的金属钛的氢化热力学函数△Hc^0，△S^0，△G^0以及平衡压力与温度的关系，与文献符合很好，这表明电子振动近似理论的可应用性，选用金属钛作为中子靶是很正确的。     

(ZnSe)n(n=1,2)团簇结构及ZnSe分子热力学性质的理论计算

用密度泛函B3LYP方法、6-311 G基组对(ZnSe)n(n=1,2)分子体系进行了理论研究,得到(ZnSe)n(n=1,2)分子体系的基态电子状态的平衡几何Re、谐振频率、偶极矩和离解能De及不同温度、压力下的热力学函数值;设用总能量中的电子和振动能量近似代表ZnSe分子处于固态时的能量,用总熵中的电子和振动熵近似代表ZnSe分子处于固态时的熵,进而计算了Zn与Se反应的ΔH0、ΔS0、ΔG0,并由此计算出不同温度的反应平衡常数Kp.结果表明:在298~1150 K温度范围内,Zn与Se反应的自由能值均为负,且随着温度的升高,ΔG0值负的越多,表明在这个温度范围内反应能自发发生,而且自发趋势随温度的升高逐渐增大;平衡常数逐渐减小,即反应进行程度随温度的升高逐渐减小;ZnSe分子材料的导电性随压力增大而增强.     

气固氢化反应热力学函数计算的近似方法

在有效原子实势近似下, 采用Gaussian 98程序及B3LYP/SDD密度泛函方法计算得到了ZrCo和ZrCoH分子的结构及能量E、熵S. 在此基础上, 近似以气态分子总能量中的振动能Ev代替该分子处于固态时的振动能量, 以电子运动和振动运动熵Sev代替分子处于固态的熵, 计算了不同温度下固态ZrCo与H2, D2, T2反应的热力学函数ΔH, ΔG, ΔS及氢化反应平衡压力, 导出了氢化反应温度与平衡压力的依赖关系. 计算得出ZrCoH, ZrCoD, ZrCoT的生成焓(398-598 K)分别为82.81 , 81.54和80.49kJ/mol, 与实验结果很好符合.     

CoH生成热力学函数的量子力学计算

用B3LYP/SDD密度泛函方法计算了CoH的微观性质、CoH(g)、CoD(g)和CoT(g)的能量 (E)和熵(S) ,进而计算Co与H2 、D2 、T2 反应的ΔH 、ΔG 、ΔS .CoH分子的基电子状态为三重态 ,Re、D 0 、ωe 分别为 1.5 2nm、2 77.84kJ/mol和 132 1cm-1,与实验值基本一致 .在固态分子的E和S的计算中 ,以气态分子计算得到的总能量中的振动能Ev 代替固态能量 ,以总熵中的电子振动熵SEv代替固态熵 .导出了Co与氢同位素气体反应的ΔH 、ΔG 、ΔS 及平衡氢压力与温度的关系 .CoH的室温下平衡离解压力很低 ,表明CoH是一种稳定的氢化物 ,这与CoH分子的D 0 很大的实验事实一致 .     

Thermodynamic Calculation on the Formation of Titanium Hydride

从钛氢化物的组成元素的基本性质出发,利用修正的Miedema生成热模型,对TiHx (1≤x≤2)的标准焓变行了计算. 采用量子力学和统计热力学的方法,计算出了TiH2的振动和电子熵,提出了一种计算TiH2标准熵变的方法. 结果表明,TiHx的标准焓变值随着x的增加呈线性关系减少. 计算得到的TiH2在298.16 K时的标准焓变值、标准熵变值以及吉布斯自由能分别为-142.39 kJ/mol、-143.08 J/(mol?K)和-99.75 kJ/mol. 计算结果与文献中实验或理论计算得到的结果均符合较好,表明所提出的钛氢化物的热力学模型是可行的.     

Al2O3X(X=H,D,T)的电子振动近似理论方法研究

用密度泛函理论(DFT)方法在6-311 G(d,p)水平上对Al2O3X(X=H,D,T)分子较低能量的几何构型进行了优化.计算结果表明该分子有两个可能基态,即Al2O3X(X=H,D,T)(2A′)Cs和Al2O3X(X=H,D,T)(2B2)C2v.全电子计算了氢同位素分子及Al2O3X(X=H,D,T)的能量E、定容热容CV和熵S.应用电子振动近似理论,即用单个分子Al2O3X(X=H,D,T)中的电子和振动能量和熵近似代表它们处于固态时的能量和熵,计算得到固体Al2O3的氢化热力学函数ΔH0,ΔS0,ΔG0以及平衡压力与温度的关系.当Al2O3吸附氢(氘,氚)形成C2v对称性气态Al2O3X(X=H,D,T)对应的固体时,氢气可以排代氘气,氘气可以排代氚气.这种排代效应非常不明显;形成Cs对称性气态Al2O3X(X=H,D,T)对应的固体时,反应的氢氘氚排代效应的顺序为氚排代氘,氘排代氢,与钛等的氢氘氚排代效应的顺序相反.总体而言,这种排代效应都非常弱.随着温度的增加,这一系列反应的氢氘氚排代效应趋于消失.     

ZnSeH分子微观性质及热力学性质的从头计算

用密度泛函B3LYP方法对ZnSeH分子体系进行了理论研究,优化得到ZnSeH分子的微观构型及不同温度下的热力学函数值.ZnSeH为角型分子,RZn-Se=0.239?5?nm、RSe-H=0.148?5?nm、角αZnSeH=94.832°.设用总能量中的电子和振动能量近似代表ZnSeH分子处于固态时的能量,用总熵中的电子和振动熵近似代表ZnSeH分子处于固态时的熵,进而计算了Zn与HSe反应的△H0、△S0、△G0,并由此计算出不同温度的反应平衡常数Kp.结果表明在298～1 098 K温度范围内,Zn与HSe反应能够自发发生,且随着温度的升高,△G0逐渐增大,平衡常数逐渐减小,自发反应进行程度越小.     

TiH(D、T)分子性质的量子力学计算

运用量子力学从头计算中的B3LYP密度泛函方法,计算了TiH(D、T)分子的结构,力学,光谱学性质和部分热力学函数,基于Debye晶格振动比热模型和Fermi-Dirac自由电子统计理论,计算了固体Ti的振动内能EV,振动和电子熵SEV,从而最终探讨了Ti吸收氢同位素气体生成一氢化物的ΔH、ΔS、ΔG以及氢同位素的平衡离解压P.结果表明:这些计算方法是可行的;在Ti吸收氢同位素生成一氢化物的反应中,ΔH、ΔS均为负值,且随温度升高,绝对值越大,ΔG则向正的方向增加;Ti的α-β转变对反应的热力学函数变化影响不大;室温直至723K,Ti的一氢同位素化物是相当稳定的;相同温度和压力下,氢置换一氢化物中的氘和氚,以及氘置换氚的反应,在热力学上有利.     

金属镍吸附氢同位素的量子力学计算

根据原子分子反应静力学与群论，确定了ＮｉＨ、ＮｉＤ和ＮｉＴ的基电子状态为２Σ＋。应用基函数６－３１１Ｇ和组态相关ＣＩ或ＱＣＩＳＤ方法，计算了氢同位素分子及其镍化物的能量Ｅ、定容热容Ｃｖ和熵Ｓ。设用总能量中的电子和振动能量近似代表ＮｉＨ、ＮｉＤ和ＮｉＴ分子处于固态时的能量，用总熵中的电子和振动熵近似代表这些分子处于固态时的熵，进而计算了镍吸附Ｈ２、Ｄ２和Ｔ２分子过程的ΔＨ°、ΔＳ°、ΔＧ°和平衡压力，并导出它们与温度的函数关系。计算指出了同位素分子效应，结果合理。所以，本文所建议的用量子力学方法计算多相化学反应，有应用参考价值。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.