三苯基咔咯金属配合物的振动光谱和DFT计算

对三苯基咔咯金属配合物(MTPC, M=Ni, Cu, Co, Mn)的拉曼和红外光谱进行了实验研究. 用DFT方法计算了其基态几何结构以及红外和拉曼光谱,并基于计算结果对测量到的振动谱带进行了局域坐标归属. 研究发现,由于对称性降低,咔咯金属配合物的振动光谱比卟啉金属配合物更为复杂,若干咔咯骨架振动与苯取代基强烈耦合.考察了拉曼和红外谱带频率变化与咔咯环结构的关系,发现随着环内核尺寸的减小,与C^I_αC^I_α键伸缩振动和C?Cm键伸缩振动相关的拉曼谱带频率增加,其中C^I_αC^I_α伸缩振动的拉曼谱带对环内核尺寸的变化更为敏感且呈良好的线性关系,可以作为反映金属咔咯骨架结构变化的特征谱带.     

四氧杂卟啉二价正离子共振拉曼光谱的TDDFT计算研究

采用DFT/TDDFF计算和极化率的态求和方法研究了四氧杂卟啉二价正离子(TOP²⁺)B态(S₂态)激发的共振拉曼(RR)光谱, 计算模型同时处理了A项和B项对拉曼极化率的贡献.用PBE1PBE、B3LYP、Cam-B3LYP、B3LYP-D3四种交换-相关泛函计算得到的RR光谱总体上相似,其中PBE1PBE和B3LYP 给出的RR 强度与实验吻合得更好一些. 对于全对称振动(A_1g),其拉曼谱带相对强度的理论计算结果与实验一致;TDDFF计算表明： 相对于基态,TOP²⁺的B态沿υ2、υ6、υ7、υ8简正模式有较大的无量纲位移, 导致相应的RR带有较大的强度. 非全对称的B_1g和B_2g 模式通过B项机理增强,其强度比A_1g模式小1～2个量级,与实验结果定性符合. 与实验相比,υ10模式(B_1g)RR强度的理论值过小,而υ11模式(B_1g)的理论值偏大;这可能是由于TOP²⁺的B-态(S₂态)具有Jahn-Teller效应.     

Resonance Raman Study of Aggregated Meso-tetra(4-pyridinium) porphyrin Diacid

研究了近激子吸收带激发下四-(4-吡啶基)卟啉二酸(H₈TPyP⁶⁺)聚集体的共振拉曼光谱．测量了H₈TPyP⁶⁺单体和聚集体的紫外可见吸收谱和共振光散射光谱．在氘代位移的基础上结合相关体系振动光谱研究,对测得的H₈TPyP⁶⁺)单体和聚集体的拉曼谱带进行了指认．聚集体的形成导致H₈TPyP⁶⁺的卟啉环CC/CN面内伸缩振动向低波数方向位移2～6 cm^-1,而卟啉环鞍形面外振动带向高波数方向位移12cm^-1．基于拉曼谱带的强度和频率变化分析了聚集引起的H₈TPyP⁶⁺分子内结构变化和分子间氢键作用     

2维SU(NC)格点规范理论中夸克真空凝聚

用改进的Wilson夸克格点哈密顿量和变分法研究2维SU(N_C)规范场中夸克真空凝聚〈ψψ〉与夸克质量m_q和Wilson参数r的依赖关系. 结果表明: 对于给定的r, 当N_C=2,3,4,5,6,7,时, 〈ψψ〉_suba/(gN_C^3/2)的值随m_q的增大而减小. 对于较大的N_C(如N_C>3), 当m_q很小时, 〈ψψ〉_suba(gN_C^3/2)对r的依赖性很小, 但随着m_q的增大, 〈ψψ〉_suba/(gN_C^3/2)对r的依赖性增大, 且〈ψψ〉_suba/(gN_C^3/2)的值随r的增大而增大; 特别是, 当m_q→0时, 本文的格点结果与Zhitnitsky的连续理论分析结果(在弱耦合相中)很好地一致, 这意味着本文在m_q≠0时所得到的结果是可靠的.     

N2第二正带系发射光谱的理论计算及实验研究

本文利用分子光谱理论系统的计算和分析N₂第二正带系(C³∏_u→B³∏_g)的发射光谱, 以研究光谱强度的分布规律与不同温度条件和气体条件的关系. 基于N₂的三重态能级结构特性, 重点计算和讨论了发射光谱的概个重要参数: 通过求解高、低电子态的哈密顿矩阵得到了振转能级特性; 利用r质心近似法求取了能级间跃迁的电偶极矩函数和爱因斯坦跃迁概率; 进而计算了不同振动和转动温度条件下谱线的强度分布. 进行了N₂和Ar的混合放电实验, 利用实验光谱数据同理论结果进行拟合分析, 确定了N₂分子的振动温度和转动温度分别约为4300 K和800 K. 另外由于潘宁离化效应, N₂浓度减小时谱线强度呈现先增强后减弱的趋势. 实验结果很好的验证了N₂第二正带系光谱理论计算的正确性.     

硫脲21A激发态扭曲几何结构的共振拉曼光谱和理论研究

获得了硫脲在水和乙腈溶液中A吸收带的共振拉曼光谱,通过B3LYP/6-311++G(3df,3pd)和RCIS/6-311++G(3df,3pd)分别对硫脲的电子跃迁和2¹A 激发态鞍点结构进行了研究．对共振拉曼光谱进行了归属,并通过含时波包理论对吸收光谱和共振拉曼光谱进行拟合,结果表明硫脲动态结构特征主要沿着：C=S伸缩振动ν₆(|△|=0.95)、H₅N₃H₆+H₈N₄H₇弯曲振动ν₅(|△|=0.19)、NCN对称伸缩振动+C=S伸缩振动+N₃H₆+H₈N₄弯曲振动ν₄(|△|=0.18)．ν₁₅倍频2ν₁₅和4ν₁₅强度主要归因于ν₁₅激发态频率的改变而不是简正模位移量的变化．对S=CN₂面外变形振动ν₁₅倍频出现的机理进行了探究,结果表明Franck-Condon区域势能面鞍点是标准A项共振拉曼散射里的二次声子机制的驱动力,导致碳原子中心的锥形化,并使硫脲在2¹A激发态发生几何结构扭曲.     

过渡金属羰基化合物Mn(CO)5Br和Re(CO)5Br结构与动力学的超快光谱

利用超快泵浦探测红外光谱、稳态线性红外光谱和计算化学方法,对过渡金属羰基化合物Mn(CO)₅Br和Re(CO)₅Br的振动和结构动力学进行了研究. 借助羰基的两个伸缩振动峰(处于低频的A₁模式和处于高频的简并E模式)进行了观测. 结果表明,在两个配合物中,A₁和E模式振动峰的振动频率位置及频率差都与中心金属原子对羰基的键级和振动力常数的影响相关. 而A₁模式比E模式的线宽宽一些,部分由于振动寿命的影响. 此外,从瞬态光谱中获得了振动模式依赖的对角非谐性常数,发现在两个羰基化合物中E模式的非谐性总是较小.     

Raman光谱方法研究三氯甲烷与苯分子间的 C/H···π相互作用

测量了不同浓度三氯甲烷(CHCl₃)与苯(C₆H₆) 二元溶液的Raman光谱,随C₆H₆浓度的增加, 受分子间C/H···π相互作用的影响, CHCl₃中C-H键伸缩振动频率向低波数移动;当 CHCl₃体积分数小于40%, C-H键伸缩振动频率不变, 分子间C/H···π相互作用达到饱和.分别以 CHCl₃和 C₆H₆体积分数为70%的 CHCl₃-C₆H₆混合溶液为研究对象, 测量了它们的高压和低温Raman光谱.根据 CHCl₃中C-H键伸缩振动频率随压强和温度的变化关系, 得出了分子间C/H···π相互作用对压强和温度的扰动表现出不稳定性.     

高分辨的一氧化二氮光解离实验研究

利用"时间切片"离子速度成像技术研究了N₂O分子在134.20、135.20和136.43 nm波长下的真空紫外光解动力学. 实验中通过采集解离产物O(¹S_J=0)的离子影像来研究O(¹S_J=0)+N₂(X¹∑_g⁺)这一解离通道. 从各个波长下的实验影像可获得产物N₂(X¹∑_g⁺)的振动态分辨的结构,进而得到产物的总平动能谱和产物N₂的振动态布居. 实验结果表明在实验的光解波长下,产物N₂(X¹∑_g⁺)主要布居在v=2和v=3. 此外,还得到了产物N₂的振动态分辨的各向异性参数β,从中发现产物N₂的β值在三个解离波长下均表现出相似的特征,即随着振动量子数的增大,β值从趋近于2逐渐减小至1.4. 这一现象表明低振动态产物是通过一个以平行跃迁解离为主的解离过程产生的,而高振动态的产物来自于一个更加弯曲的中间构型的解离. 此推论与在平动能谱中所见到的最强转动态布居随着振动量子数的增大而出现的位移是相一致的.     

胸腺嘧啶低能量VUV光解离路径的实验和理论研究

利用同步辐射真空紫外光电离质谱和理论计算研究了胸腺嘧啶的光解离反应路径, 通过改变光子能量得到不同的质谱信号, 光子能量在12.0 eV时主要的碎片有m/z=98 (C₄H₆N₂₄O⁺)、97 (C₄H₅N₂O⁺)、84 (C₃H₄N₂O⁺或C<     

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.