基于溴取代基的多溴联苯醚同系物红外光谱特征振动辨识研究

借助密度泛函理论采用B3LYP/6-31G(d)方法对209种多溴联苯醚(PBDEs)同系物进行了结构优化和频率计算,利用已知的PBDEs结构和频率参数值对计算结果进行验证,平均模拟系数为0.989。在此基础上,选取苯环上只有H原子或Br取代基且红外光谱各振动形式间干扰较少的二苯醚和BDE-209为代表,分别对PBDEs的苯环振动和C—Br振动进行归属。研究发现苯环三角呼吸振动具有普遍性、强振动性和可区分性,而红外光谱中C—Br振动常与其他振动形式相耦合不易区分,故选取苯环三角呼吸振动作为PBDEs同系物的特征振动,以分析其振动频率与溴取代基之间的规律。研究结果表明:邻对位取代基可显著提高苯环三角呼吸振动频率,间位取代基作用相反;低溴代物中邻位取代基越多特征振动频率越高,而高溴代物中同时存在邻对位取代基的同系物频率较高;取代类型相同时,位于同一苯环取代基数越多的同系物振动频率较高。利用SVM回归模型对溴取代基与苯环三角呼吸振动频率间变化规律进行模拟,所建模型的模拟效率系数为0.956,说明所建分析方法可为红外光谱检测和辨别PBDEs同系物提供一定的理论基础。     

基于含时密度泛函理论的对位卤代二苯醚电子跃迁机理

以二苯醚（DE）为参照物,借助Gaussian软件的量子化学计算并结合自然键理论与跃迁密度矩阵平面图对9种对位卤代二苯醚的基态分子活性、紫外光谱及基态-激发态电子跃迁机理进行了对比分析。研究结果表明：处于基态时的DE与4,4’-二氯二苯醚（CDE-15）分别最易发生亲电/核反应,对位卤代基的引入缩小了DE的能级差。随着取代基体积的增大,对位取代二苯醚紫外光谱的最大吸收波长变大,吸收增强。所研究的10种物质有着相似的跃迁机理。     

红外光谱中取代基对苯环骨架振动吸收峰的影响规律

本文初步地探讨了单取代及对位双取代对苯环骨架振动吸收峰频率和强度的影响规律 ,得出结论 :1给电子单取代基随给电子能力增强使苯环骨架振动吸收峰 16 0 0 cm-1增强 ,而吸电子基则相反。 2卤素作为单取代基时 ,使苯环骨架伸缩振动产生强红外吸收峰 ;且随卤素电负性增强吸收峰频率向高波数移动。 3对位取代基为不同类型时 ,16 0 0 cm-1处显强峰 ,而为同一类型时 ,当电子效应相近或相同时 ,16 0 0 cm-1处吸收峰很弱或根本无吸收峰。并讨论了产生这些现象的原因。     

氯代5-氟脲嘧啶卟啉的红外光谱特性的研究

本文对新合成的对位及间位两类氯代苯基 5 氟脲嘧啶卟啉的红外光谱吸收峰进行了归属和总结 ,讨论了其红外吸收频率随取代基位置变化的规律。指出了苯环上的取代基为电负性强的基团时 ,由于场效应的存在 ,使被测化合物的羰基伸缩振动吸收峰的相对强度发生改变。同时 ,表明了嘧啶环上N原子发生了取代 ,形成单、双取代 5 氟脲嘧啶卟啉化合物的红外光谱特性。     

分子振光谱中的吸电子效应和供电子效应

本文就分子振动光谱中的吸电子效应和供电子效应提出了新观点：对共价键来说，吸电子效应使化学键强度增加，因而伸缩振动频率升高；供电子效应使供价键强度减弱，因而伸缩振动频率降低。对于配价键而言，如果取代基和配价键中提供电子对的原子相连，则供电子取代基使配价键加强，因而配价键的伸缩振动频率升高；吸电子取代基使配价键减弱，因而其伸缩振动频率降低。如果取代基和配价键中的受电子原子相连，则取代基的电子效应正好相     

卤素驱动石墨二炔带隙的打开以实现光催化全解水

本文通过杂化密度泛函理论研究了卤素(F、Cl和Br)功能化的石墨二炔的能带结构. 结果表明修饰的石墨二炔的带隙能随着卤素原子对的增加而增加;同时,价带顶的位置受卤素原子电负性大小的影响：当石墨二炔表面的卤素原子数目相同时,卤素原子的电负性越大,改性后石墨二炔的价带顶的位置越深. 另外,计算结果表明石墨二炔的带隙可以通过不同卤素原子的适当混合修饰来有效调节,不同卤素原子混合修饰的石墨二炔的价带底和导带顶跨越了水的氧化还原电位. 通过热力学分析进一步证明,不同卤素原子混合修饰的石墨二炔比单一卤素修饰的石墨二炔表现出更好的光催化水全解反应活性. 这项工作对于如何设计更高效的全解水光催化剂提供了洞见.     

(Fe,N)共掺杂TiO2红外光谱的电负性原理研究

采用电负性原理,构建合理的红外光谱模型,对TiO2红外光谱的振动频率与元素电负性之间的各种经验关系进行探究.采用溶胶-凝胶法制备(Fe,N)共掺杂TiO2,利用X-射线衍射(XRD)、傅里叶红外光谱(FTIR)对样品的物相和红外光谱进行了表征.XRD物相分析表明当煅烧温度为600 ℃时,TiO2样品中的无定形结构己基本转化为锐钛矿型结构.随着煅烧温度升高,TiO2的X射线衍射峰逐渐由宽变窄,衍射强度由弱变强.当煅烧温度为700 ℃时,锐钛矿型的衍射峰基本消失,取而代之的是金红石相的衍射峰,但TiO2的主晶相并没有发生改变.红外光谱分析表明(Fe,N)共掺杂TiO2在650~500 cm-1区间有一个较宽的吸收峰.电负性模拟计算了(Fe,N)共掺杂TiO2红外光谱的伸缩振动频率,获得了Fe、N掺杂的位置、分子结构和键价特征:首先计算出约化质量μ,然后按照经典力学伸缩力常数k与频率V之间满足的关系,结合力常数与电负性关系、键级的计算方法,计算了基本单元都是氧八面体的掺杂金红石、锐钛矿TiO2的分子振动频率.结果表明:通过电负性理论计算的(Fe,N)共掺杂的TiO2的红外光谱与实验测量的红外光谱的伸缩振动频率比较吻合.     

(Fe,N)共掺杂TiO_2红外光谱的电负性原理研究（英文）

采用电负性原理,构建合理的红外光谱模型,对TiO_2红外光谱的振动频率与元素电负性之间的各种经验关系进行探究。采用溶胶-凝胶法制备(Fe,N)共掺杂TiO_2,利用X-射线衍射(XRD)、傅里叶红外光谱(FTIR)对样品的物相和红外光谱进行了表征。XRD物相分析表明当煅烧温度为600℃时,TiO_2样品中的无定形结构己基本转化为锐钛矿型结构。随着煅烧温度升高,TiO_2的X射线衍射峰逐渐由宽变窄,衍射强度由弱变强。当煅烧温度为700℃时,锐钛矿型的衍射峰基本消失,取而代之的是金红石相的衍射峰,但TiO_2的主晶相并没有发生改变。红外光谱分析表明(Fe,N)共掺杂TiO_2在650~500cm-1区间有一个较宽的吸收峰。电负性模拟计算了(Fe,N)共掺杂TiO_2红外光谱的伸缩振动频率,获得了Fe、N掺杂的位置、分子结构和键价特征:首先计算出约化质量μ,然后按照经典力学伸缩力常数k与频率ν之间满足的关系,结合力常数与电负性关系、键级的计算方法,计算了基本单元都是氧八面体的掺杂金红石、锐钛矿TiO_2的分子振动频率。结果表明:通过电负性理论计算的(Fe,N)共掺杂的TiO_2的红外光谱与实验测量的红外光谱的伸缩振动频率比较吻合。     

卤素驱动石墨二炔带隙的打开以实现光催化全解水（英文）

本文通过杂化密度泛函理论研究了卤素(F、Cl和Br)功能化的石墨二炔的能带结构.结果表明修饰的石墨二炔的带隙能随着卤素原子对的增加而增加;同时,价带顶的位置受卤素原子电负性大小的影响;当石墨二炔表面的卤素原子数目相同时,卤素原子的电负性越大,改性后石墨二炔的价带顶的位置越深.另外,计算结果表明石墨二炔的带隙可以通过不同卤素原子的适当混合修饰来有效调节,不同卤素原子混合修饰的石墨二炔的价带底和导带顶跨越了水的氧化还原电位.通过热力学分析进一步证明,不同卤素原子混合修饰的石墨二炔比单一卤素修饰的石墨二炔表现出更好的光催化水全解反应活性.这项工作对于如何设计更高效的全解水光催化剂提供了洞见.     

亚锗基卡宾及取代亚锗基卡宾与环氧乙烷抽提反应机理的密度泛函理论研究

采用B3LYP/6-311G(d,p)方法研究了单重态亚锗基卡宾及取代亚锗基卡宾X₂Ge=C:(X=H, F, Cl, CH₃)与环氧乙烷的氧转移反应机理. 结果表明, 由于环氧乙烷中氧上的2p孤对电子向X₂Ge=C:中C上的2p空轨道迁移,形成了p→p授受键,从而生成了各中间体. 随着p→p授受键的不断加强(即C-O键的逐渐缩短),中间体经过渡态生成了抽提产物. 取代基的电负性是影响该类反应的主要因素,取代基的电负性越大,反应的活化能越小     

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.     

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.     

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.