用稳定变分方法计算锂原子电多极极化率和两体色散系数北大核心CSCD

以最弱受约束电子模型理论(WBEPM)所得到的锂原子基态波函数为基础,利用Gao和Starace提出的稳定变分方法,计算了锂原子的电多极极化率和锂-锂体系的两体色散系数,计算结果与已有文献吻合,但计算方法更为简化且便于推广到其他碱金属原子.     

锂原子的高激发态能级计算及其在微波场中的布居动力学过程

利用B样条技术,设计了一种计算高激发原子能级结构的方法,计算了高激发锂原子的能级结构,并研究了里德堡锂原子在微波场中的布居动力学过程。     

锂原子多激发态的能量与辐射寿命

采用马鞍点变分方法截断变分方法和马鞍点复数转动技术，计算分析了锂原子双激发和三激发态的能量和波函数，并计算了位移、Ａｕｇｅｒ宽度、相对论修正和质量极化效应。另外，还计算了锂原子的一电子跃迁、二电子跃迁和三电子跃迁的辐射跃迁率。计算结果与实验值符合得很好。     

类锂原子基态能量的双参数微扰法研究

提出了一种计算类锂原子基态能量的双参数微扰法.用该方法计算出的类锂原子(质子数Z=3-10)基态一级近似能量与实验值非常吻合,相对误差在0.2%之内.     

碱金属原子振子强度的核实极化效应

为了突出考虑碱金属原子中价电子和原子实的关联,作者在文献[2]的基础上又引入了核实偶极极化势。由此,本文对原子锂、钠及类锂原子系列共振跃迁的振子强度和跃迁能就该势引入前后作了相应的对比计算。结果表明,在振子强度的X_a过渡态计算模式下,引入核实极化效应,对于碱金属原子最主要的共振跃迁的振子强度计算有显著改进。     

关键参数对锂原子光致漂移速率影响的数值研究

光致漂移速率是用来衡量光致漂移效应大小的重要参数,对光致漂移研究具有重要意义。利用强碰撞模型描述光致漂移过程中锂原子与缓冲气体的碰撞作用,并考虑了超精细结构和能级简并对光致漂移过程的影响,通过建立速率方程来表示不同速度的锂原子在各能级上的布居,从而获得锂原子的漂移速率。同时研究了激发光波长、激发光功率密度、缓冲气体压强、缓冲气体种类、气体温度等对锂光致漂移速率的影响。由理论计算结果可以看出,利用该方法计算所得的漂移速率随各参数的变化关系基本符合光致漂移的物理原理分析和相关文献中的实验结果规律。     

锂原子能量的近似解

本文用屏蔽库仑势模型将锂原子的哈密顿量加以简化，然后用微扰法求解了锂原子一系列能级值，计算简洁，结果也与实验值符合得很好。     

锂洞原子双激发态的鞍点能量计算

采用鞍点截断变分方法和鞍点复数转动技术,计算和分析了锂洞原子双激发共振态[1s(2s2p)3P]2P0的鞍点能量和波函数.计算结果表明这种理论计算方法是获得高精度的能量值的重要保证.     

FC PC 方法在计算类锂原子体系时的应用

用FCPC（Full core plus correlation）方法计算具有1s2原子实的类锂原子体系能级结构。并用FCPC方法计算了Sc18＋的1s2 nd态的电离能和激发能,结果显示,理论计算值与实验值相符（在误差范围之内）。     

平行电磁场中的Rydberg锂原子吸收谱的模型势计算

用B样条基组展开方法结合模型势计算了Rydberg锂原子在平行电磁场下的振子强度谱. 径向和角向均采用高阶Ｂ样条基组.计算结果与已有的实验结果符合得很好.利用分波分析法,对部分谱线的振子强度的强弱进行了分析. 本文方法简单有效，易于推广到交叉电磁场中Rydberg原子的精确谱的计算. 关键词： B样条 能谱 振子强度 平行电磁场 Rydberg原子     

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.     

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.     

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.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.     

Fiber Modal Index Measurements Based on Fiber Gratings

A novel method based on fiber gratings for measuring the effective indices of fiber modes is proposed. The effective index difference between the core mode and a cladding mode was obtained by analyzing the interference fringe of a pair of cascaded long-period fiber gratings. In order to extract the core mode index from the measured index difference, an index matching oil immersion method is proposed. By analyzing the interaction between the cladding mode and the oil applied on the cladding surface, the mode order and the effective index of the involved cladding mode might be calculated. Experimental results about the interference fringe shifts induced by the oil index and the oil-applied length are also presented.     

Optical Pulse Compression Schemes That Use Nonlinear Bragg Gratings

Nonlinear optical pulse compression of picosecond pulses typically requires long lengths of optical fiber and multiple components. Periodic structures, such as fiber Bragg gratings, are highly dispersive at wavelengths outside of the photonic bandgap. This implies that such gratings can be used as very short all-fiber compressors. In this paper a number of such compression schemes are reviewed involving uniform and nonuniform fiber Bragg gratings, relying on both soliton and nonsoliton compression principles. Experimental results supporting the corresponding underlying theory are also presented. Finally, an extension of one of the compression schemes is shown, which allows the generation of adjustable high-repetition rate soliton trains.