锕系双原子分子的从头算研究

用相对论有效原子实势（RECP）和密度泛函方法（B3LYP）,采用U和Pu原子的紧缩价基集合[5s4p3d4f]/[3s3p2d2f],优化了U2和Pu2分子的平衡结构,得到它们的键长（LBL）和短键长（SBL）分别为：U2分子是0．38965和0．29927nm,Pu2分子是0．45375和0．35202nm;导出了基态和最低激发态的势能函数,计算出它们的力常数、光谱数据和离解能。     

Ar原子偶宇称3p5(2P1/2)nl′ [K′]J (l′=1, 3)自电离Rydberg态共振增强激发光谱

用脉冲直流放电产生Ar原子亚稳态3p⁵4s[3/2]₂和3p⁵4s′[1/2]₀．在单光子32500～35600 cm^-1能量范围内, 结合飞行时间质谱技术获得Ar原子共振增强激发光谱．光谱分析表明,所有谱线来源于Ar原子3p⁵4s[3/2]₂和3p⁵4s′[1/2]₀两个亚稳态吸收单个光子向偶宇称np′、nf′自电离Rydberg态序列的跃迁．实验观测到许多新的自电离能级,并获得更精确和系统的能级位置和量子亏损值数据．     

He-H2S复合物的六维从头算势能面和束缚态

采用[CCSD(T)]-F12a/aug-cc-pVTZ方法,同时在基组中引入中心键函数(3s3p2d1f1g)构建了He-H$_2$S复合物的高精度六维势能面. 除分子间振动坐标,同时考虑了H₂S分子内的v₁对称伸缩振动Q₁正则模、v₂弯曲振动Q₂正则模和v₃反对称伸缩振动Q₃正则模三种振动模式. 将计算得到的六维势能面在Q₁,Q₂和Q₃方向上分别做积分得到H₂S单体分别处于振动基态、v和v₃激发态下的He-H₂S的三个振动平均势能面. 计算结果表明,每个平均势能面都有一个T形全局极小值、一个平面局部极小值、两个平面内鞍点和一个平面外鞍点. 全局极小值的几何构型位于R=3.46 ?,θ=109.9°和φ=0.0°,势阱深度为35.301 ^-1. 在径向部分采用离散变量表象法和角度部分采用有限基组表象法并结合Lanczos循环算法计算了He-H₂S的振转能级和束缚态. 计算发现He-(para-H₂S)在H₂S的v₂和v₃区域的带心位移分别为0.025 cm^-1和0.031 cm^-1,而He-(ortho-H₂S)的带心位移分别为0.041 cm^-1和0.060 cm^-1,都表现为蓝移.     

0.5NdAlO3-0.5CaTiO3电子结构及光学性质的第一性原理计算

采用基于第一性原理密度泛函理论的平面波赝势方法,对0.5NdAlO₃-0.5CaTiO₃晶体进行结构优化,并对其能带结构,态密度和光学性质进行了理论计算.结构优化后晶格参数与实验数据相符合,误差小于1%;能带计算结果表明0.5NdAlO₃-0.5CaTiO₃为间接带隙,带隙值为0.52eV;费米面附近的能带由Nd-4f,O-2p,Nd-4p,Al-3p,Ti-4d层的电子态密度确定.同时也计算了该结构的介电函数,反射率和复折射率等光学性质.     

CUO分子结构与势能函数

用密度泛函理论的B3LYP方法,对铀原子采用14个价电子的准相对论有效原子实势及(6s5p2d4f)[3s3p2d2f]收缩价基集合,碳、氧原子采用6311G全电子基集合,应用Gaussian98程序对一氧化碳气体与铀表面相互作用的可能分子结构CUO(角形Cs和线形C∞v构型)分子进行几何优化计算,得到了稳定结构的几何构形、能量、谐振频率、力学性质和电性质,并用微观可逆性原理分析了其可能的离解极限.结果表明,势能函数等值势能面图能清晰地再现CUO分子的结构特征和离解能;铀原子与一氧化碳的反应是势垒较低、容易进行的反应 关键词： CUO 密度泛函理论 分子结构 势能函数     

第一性原理研究LuAlO3中掺杂Ce3+的4f-5d跃迁性质

通过对基态4f电子采用杂化密度泛函理论方法、对5d激发态采用限制性布居方法,研究了LuAlO₃:Ce³⁺体系4f-5d跃迁的相关性质．结果表明,伴随着4f到5d的跃迁,Ce³⁺与8个最近邻配位O原子的平均键长缩短了0.05 ?,而且Stokes位移计算值与实验值相当吻合．在优化计算得到的LuAlO₃:Ce³⁺体系4f基态局域构型基础上,采用角重叠模型计算了5d能级的晶场分裂,与实验结果吻合较好.     

小尺寸VmOn+团簇的激光光解和密度泛函计算

通过激光溅射法产生了V₂O_n⁺ (n=1, 2), V₃O_n⁺ (n=1, 2, 3)和V₄O₃⁺等缺氧的钒氧团簇,并采用532和266 nm波长的激光对它们进行了光解研究. 利用密度泛函理论计算与激光光解实验相结合确定了这些团簇的几何结构和可能的光解通道. 激光光解实验表明V相似文献   

Ca3Sc2Si3O12:Ce3+的第一性原理研究

对Ca₃Sc₂Si₃O₁₂:Ce³⁺共掺杂N^3-、Sc³⁺、Mn²⁺、Mg²⁺和Na⁺进行第一性原理计算,研究不同的电荷补偿对发光中心Ce³⁺的影响．首先利用密度泛函理论构建超晶胞模型对Ce³⁺周围的局部结构进行了优化,然后通过CASSCF/CASPT2 RASSI-SO计算得到Ce³⁺的4f→5d跃迁能量．计算数据与实验光谱相吻合．实验光谱中的一个未知峰值理论分析确认是Sc³⁺替代Si⁴⁺导致的．     

TiN分子基态(X2Σ)结构和势能函数

应用群论及原子分子反应静力学方法推导了TiN分子基态(X²Σ )的离解极限. 采用不同的密度泛函方法,包括BP86, B3P86, B3LYP, B3PW91, 分别选用不同的基组对TiN分子基态进行结构优化计算.通过比较得出使用BP86方法, 对N原子使用D95V++(d,P)基组和Ti原子使用6-311++G^**基组时,计算得到的平衡几何结构、 分子离解能和谐振频率与实验值符合得最好. 并采用最小二乘法拟合改进的Murrell-Sorbie函数得到了相应电子态的完整势能函数. 计算得到的光谱常数与实验光谱数据符合得很好.     

M’型GdTaO4电子结构的第一性原理研究

运用基于密度泛函理论的赝势平面波方法计算了M’型GdTaO₄的电子结构.结果表明：M’型GdTaO₄价带顶主要由O-2p电子构成,导带底由Ta-5d的e轨道电子构成;当U_eff=8 eV时,自旋向上和自旋向下的Gd-4f电子分别局域于价带顶以下627 eV和导带底以上301 eV处;计算得到M’型GdTaO₄的折射率为224,与应用半经验的Gladstone-Dale关系得到的结果符合得很好.     

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.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

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.     

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.     

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.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.