He同位素原子与HBr分子碰撞的微分截面

基于作者构造的He-HBr体系的各向异性势,采用密耦方法计算了³He,⁴He,⁶He和⁷He与HBr分子在碰撞能量分别为40和75meV时的微分截面,详细讨论了入射氦同位素对微分截面的影响.结果表明：在相同碰撞能量时,随着同位素氦原子质量的增加,总微分截面在0° 时的角分布逐渐增大,同一级衍射振荡极小值位置逐渐向小散射角方向移动;弹性与总非弹性截面交界角逐渐减小,总非弹性截面逐渐增加.碰撞能量越低,入射同位素He原子的 关键词： 同位素效应 微分截面 各向异性势 He-HBr体系     

He同位素对He-NO碰撞体系微分截面的影响

用密耦近似方法计算了同位素He原子与NO分子碰撞体系的总微分截面、弹性微分截面和非弹性微分截面,总结了同位素He原子对He-NO碰撞体系微分截面的影响. 计算结果表明：在同一入射能量下,随着入射同位素He原子质量增加,总微分截面在0°时的角分布逐渐增大;同位素He原子与NO分子碰撞发生的彩虹现象越明显. 同时,体系约化质量增加的效应大于相对碰撞速度减小的效应,使散射振荡间隔逐渐减小. 关键词： He-NO 密耦近似 微分截面 同位素效应     

3He4He与H2分子碰撞的同位素效应研究

用公认精确度较高的密耦近似方法计算了入射能量E=0.5eV时惰性气体原子3He(4He)与H2分子替代碰撞体系的转动激发碰撞截面.通过分析3He(4He)-H2碰撞体系分波截面和微分截面的差异,总结出在氦原子的同位素替代情形下3He(4He)-H2碰撞体系分波截面和微分截面随分波数增加和同位素原子质量改变的变化规律.     

He-BH碰撞体系微分截面的理论计算

用公认精确的密耦近似方法计算了入射能量从25至150 meV时,He原子与基态BH分子碰撞的弹性微分截面、非弹性微分截面和总微分截面,进一步讨论了微分截面的变化趋势及特征.计算结果表明：He-BH碰撞体系的总微分截面具有原子与双原子分子散射的一般规律和特征;随着入射能量的增加,低转动激发态-态微分截面在大角区的散射振荡现象会更加明显. 关键词： He-BH复合物 相互作用势 密耦近似 微分截面     

不同能量下He原子与HCl分子碰撞激发分波截面的同位素效应研究

基于Huxley势函数的拟合势,通过精确度较高的密耦近似方法计算了入射能量为50meV和150meV时,氦原子的四种同位素3He,4He,9He,10He与HCl分子碰撞体系的激发分波截面.通过分析不同能量下,各碰撞体系分波截面的差异,探讨了不同入射能量时He的同位素对He-HCl碰撞体系的分波截面的影响,总结出其分波截面随量子数和体系约化质量的变化规律.     

不同能量下He原子与HCl分子碰撞激发分波截面的同位素效应研究

基于Hux1ey势函数的拟合势,通过精确度较高的密耦近似方法计算了入射能量为50 meV和150meV时,氦原子的四种同位素3He,4He,9He,10He与HCl分子碰撞体系的激发分波截面.通过分析不同能量下,各碰撞体系分波截面的差异,探讨了不同入射能量时He的同位素对He-HCl碰撞体系的分波截面的影响,总结出其分波截面随量子数和体系约化质量的变化规律.     

非对称同位素替代分子HD、HT和DT分子与氦原子(E=0.1 eV) 碰撞角分布计算

当入射氦原子能量E=0.1 eV时,用密耦方程(Close Coupling Equation)计算非对称同位素替代分子HD、DH-He碰撞的弹性和非弹性散射的角分布.     

惰性气体原子与氢的同位素分子T2碰撞分波截面计算

用密耦计算方法及T.T(Tang-Toennies)势模型分别计算了入射能量E=0.05 eV、0.15 eV、0.25 eV时He、Ne、Ar、Kr、Xe-T2碰撞体系的00-00弹性碰撞和00-02非弹性碰撞分波截面,结果表明:对00-00弹性碰撞,分波截面随量子数J的增加不断振荡, 并随入射原子的相对碰撞能量的变化,振荡极大值的位置、收敛分波数等均有不同的变化.     

61.8MeV~(12)C在~(27)Al上的深部非弹性碰撞研究

用△E-E望远镜技术和飞行时间技术对61.8MeV的~(12)C离子轰击~(27)Al靶的反应测量了从~6Li到~(16)O的诸同位素能谱。得到了质心系微分截面等高图及出射碎片角分布。从而得到轻系统深部非弹性碰撞过程的能量全弛豫值,并在耗散模型框架中,通过实验的能量全弛豫值与理论值的比较,得到了出射道的库仑能、核势能与转动能各自的贡献。通过理论拟合角分布,得出双核系统平均相互作用时间在1×10~(-21)—1.4×10~(-22)秒之间,得到了出射碎片分离时的最接近距离的参数值。通过势能面的计算,说明了出射产物产额的变化趋势。并从总产物角分布分解出准弹性截面及深部非弹性截面数值。     

He原子与HI分子碰撞截面的密耦计算

基于发展的分子间相互作用势, 采用密耦方法计算了入射能量从1到140?meV范围内He原子与HI分子碰撞的微分截面、分波截面和积分截面.通过与He-HX（X=F,Cl,Br）体系分波截面的比较, 印证了He-HI体系相互作用势以及密耦计算结果的可靠性.结果表明：小角散射的概率大于大角散射的概率;碰撞能量越高,散射概率就越小, 尾部效应也越弱.总积分截面主要来自弹性碰撞的贡献;非弹性积分截面以00→01和00→02跃迁的贡献为主,其中00→02跃迁的贡献最大. 关键词： 碰撞截面 密耦计算 HI-He体系     

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.     

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.     

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.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.