Theoretical Study on Mechanism of Reaction of OH with HO2NO2

运用密度泛函的B3LYP方法及CBS-QB3方法对HO2NO2(过氧硝酸,PNA)与OH自由基的反应进行了理论研究. 结果表明, 在计算所得的势能面曲线上存在五个产物通道,分别为H2O+NO2+O2、HOOH+NO3、NO2+HO3H、HO2+HONO2和HO2+HOONO. 对这五个通道分别进行了详细的研究,其中最主要的反应通道为：PNA+OH!M1!TS1!H2O+NO2+O2. 采用了一个准平衡近似的方法并运用CBS-QB3基础上的能量计算得到了300K下此反应路径的速率常数值为1.13 ￡10-1     

HOD分子在?1B1态的光解动力学： 产物OH/OD的分支比以及OD键解离能

利用H(D)原子里德堡态时间飞渡谱技术研究了HOD超声射流分子束在124 nm附近的?态光解动力学．实验测量了HOD分子在?态的转动分辨的吸收谱,并得到了五个转动峰下H+OD以及D+OH通道的产物总的平动能谱．通过对产物平动能谱的分析,得到了?态解离产物OH和OD的分支比,并与Β态和?态相应解离产物的分支比做了对比．实验结果确定了HOD分子OD键的解离能为41751.3±5 cm^-1.     

N2O+离子A2∑+电子态的光解动力学研究

用一束波长为360.55nm的激光,通过N2O分子的(3+1)共振多光子电离(REMPI)过程制备纯净且布居完全处于X2Ⅱ(000)态的母体离子N2O+,然后用另一束波长在275-328nm范围内的可调谐激光将制备的N2O+离子激发至预解离电子态A2∑+.实验发现,由于解离碎片NO+所具有的一定的反冲速度,其TOF质谱峰明显比N2O+母体宽.通过分析NO+碎片TOF质谱峰形状,得到了解离产物的总平均平动能;通过考察随光解能量的变化,发现光解能量在32000cm-1附近约250cm-1的变化范围内,值由约8000cm-1突然减小至约1600cm-1.通过分析,在光解能量小于32000cm-1的区域,解离通道为NO+(X1∑+)+N(4S);而在光解能量大于32000cm-1的区域,另一个具有较高解离限的解离通道,NO+(X1∑+)+N(2D),开启并完全取代N(4S)通道成为解离的惟一通道.根据实验结果,对在所研究的光解能量范围内的N2O+离子A2∑+电子态预解离机理进行了探讨.     

高温下黑索金（RDX）热分解动力学模拟

应用分子动力学模拟方法研究了黑索金(RDX)在纯高温下的分解机理, 研究结果表明RDX初始分解机理主要为N-N键的断裂形成NO2分子, 然后发生H原子转移反应形成H2O, HONO, HO和NO分子; 通过对RDX热分解反应物和生成物的研究结果表明N2和H2O分子是RDX分解过程中最稳定的生成物, NO2, HNO3, NO, NO3和HONO分子为RDX热分解过程中的中间产物; 在高温4500K, CO, CO2和OH分子出现的频率逐渐提高, 表明这几种分子在高温下更容易形成.     

高温下黑索金（RDX）热分解动力学模拟

应用分子动力学模拟方法研究了黑索金(RDX)在纯高温下的分解机理, 研究结果表明RDX初始分解机理主要为N-N键的断裂形成NO2分子, 然后发生H原子转移反应形成H2O, HONO, HO和NO分子; 通过对RDX热分解反应物和生成物的研究结果表明N2和H2O分子是RDX分解过程中最稳定的生成物, NO2, HNO3, NO, NO3和HONO分子为RDX热分解过程中的中间产物; 在高温4500K, CO, CO2和OH分子出现的频率逐渐提高, 表明这几种分子在高温下更容易形成.     

Photodissociation Dynamics of Methanol and Ethanol at 157 nm

利用氢原子里德堡时间飞行谱技术研究了超音速喷射分子束CH3OH和C2H5OH在157 nm的光解动力学,得到了氢原子产物的时间飞行谱．通过对谱图的拟合揭示出三个氢原子产物通道：OH上的氢原子脱落、CH3(C2H5)上的氢原子脱落和CH3O(C2H5O)的二次解离． 从得到的产物通道相对分支比可以知道CH3O的二次解离过程比C2H5O更明显．CH3OH解离的产物平均角分布各向异性参数β≈-0.3, 显示出跃迁偶极距接近垂直于C-O-H平面．C2H5OH解离的产物β≈-0.4,表明C2H5OH有更长的转动周期． 实验结果显示两个系统都经历了从3px到3s势能面的快速内转换, 然后在3s势能面上解离．CH3O+H产物平动能分布显示出CH3O的伞形振动激发或者CH3的摇摆振动激发,而C2H5O+H产物平动能分布没有振动态分辨．     

CH(X~2∏)+N_2O的反应机理研究

在G2 (B3LYP/MP2 /CC)理论水平上研究了CH(X2 ∏ )自由基与氧化二氮 (NNO)分子的反应 .计算了反应体系的最低二重态势能面上各驻点的构型参数、振动频率和能量 ,揭示了此反应存在两种机理和六个通道 .其中HC和NNO复合 ,生成中间体HC(N)NO ,解离得到产物HCN +NO ,这是最主要的通道之一 ;HC插入NO键 ,克服 38.9kJ/mol的势垒 ,产生富能的中间体HC(O)NN ,预测了五个反应通道 ,其中主要反应通道为 :NN +HCO .     

H_2O分子在HONO+OH→NO_2+H_2O反应中的催化机制研究

本文采用CCSD(T)-F12a/cc-p VDZ-F12//M06-2X/6-311+G(2df,2p)方法并结合过渡态理论对HONO+OH→H_2O+NO_2抽氢反应以及H_2O参与该反应的微观机理和速率常数进行了理论研究.结果表明,由于复合物HONO…H_2O的高浓度和稳定性,我们预测HONO…H_2O+OH反应的大气相关性将比H_2O…HONO+OH和H_2O…OH+cis-HONO明显得多.进一步的速率常数计算结果表明,cisHONO…H_2O+OH反应的速率常数比H_2O…cis-HONO+OH和H_2O…OH+cis-HONO反应大了8～4个数量级.然而,cis-HONO…H_2O+OH反应的有效速率常数比无催化剂主反应cis-HONO+OH低了7～3个数量级.表明在实际大气环境中,H_2O对HONO+OH反应的催化效果并不明显.     

CH(X2∏)+N2O的反应机理研究

在G2(B3LYP/MP2/CC)理论水平上研究了CH(X^2Ⅱ)自由基与氧化二氮（NNO）分子的反应。计算了反应体系的最低二重态势能面上各驻点的构型参数、振动频率和能量，揭示了此反应存在的两种机理和六个通道。基中HC和NNO复合，生成中间体HC(N)NO，解离得到产物HCN+NO，这是最主要的通道之一；HC插入NO键，克服38.9kJ/mol的势垒，产生富能的中间体HC(O)NN，预测了五个反应通道，其中主要反应通道为：NN+HCO.     

OCS分子在207 nm的光解动力学研究:S(~1D_2)+CO(X~1∑~+)产物通道（英文）

利用直流时间切片离子成像技术对OCS分子在紫外波段207nm的光解产物S(~1D_2)进行了偏振实验研究.通过在两种不同的共振增强多光子电离中间态,~1F_3和~1P_1,以及四种不同的泵浦-探测激光偏振几何构型下探测了光碎片S(~1D_2)的角动量极化特性.使用分子坐标系极化模型和实验室坐标系各向异性模型提取和分析出对应产物CO(X~1∑~+)的角分布.观测到的总平动能释放谱表明解离过程存在三种解离通道,分别对应于低、中、高平动能解离通道.低、中平动能通道的来源与光解波长在较长波长下得到的双峰分布来源一致.高平动能通道是一种新的解离通道,它来自于单重排斥态A(2~1A')的直接解离.     

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.