含氟聚合物交联度的XPS表征

本文研究了用X-光电子能谱(XPS)求F-46(四氟乙烯—六氟丙烯共聚物),含氟聚酰亚胺和聚偏氟乙烯的凝胶化剂量(Rg),并表征其交联度。目前交联的含氟聚合物的XPS研究,特别是用它表征交联度还未见文献报告。实验结果表明这些含氟聚合物的辐射交联是通过脱氟原子进行的,其F/C(氟原子与碳原子比)必然随交联度的增加而下降,从而与其交联度相关。以交联样品的logF/C对logR(辐照剂量)做图,或以logⅠ(含氟原子碳基团的Cls峰的相对强度)对logR做图,可以求得Rg值。用XPS方法和凝胶含量方法求得的Rg值较一致。     

CO与K在Fe(110)面上共吸附的角分辨紫外光电子谱

用角分辨偏振紫外光电子谱对CO与K在Fe(110)表面上共吸附进行了研究。CO与K共吸附的Hel紫外光电子谱与清洁表面上CO的结果相比,在结合能为6.3eV处出现了一个新的谱峰。偏振紫外光电子谱的分析表明:相关的初态有一对称面,此面平行于衬底〈001〉方向。Hell紫外光电子谱中,CO的4σ态(4α₁)强度随入射角改变的结果表明CO依然近似于直立在有K覆盖的Fe表面上。 关键词：     

小檗碱和9-O取代衍生物紫外光谱及构效研究

在水溶剂中,采用含时密度泛函理论(TD-DFT)和Multiwfn波函数分析软件中空穴-电子分析探究小檗碱及其衍生物紫外光谱电子激发特征,进而讨论构效关系。理论紫外光谱与实验光谱吻合较好,其中243 nm和416 nm处的两个吸收峰可认为是与小檗碱及其衍生物药性相关的特征吸收峰。小檗碱9-O处3-溴代丙基的取代不仅未引起吸收峰位置的变化,且提高O供电子能力,增强吸收峰强度;而2-氯代乙酰基、2-溴代乙酰基、环丙沙星的取代使9-O处氧对小檗碱母体无供电子能力,导致吸收峰红移。a、b环及9-O处氧是小檗碱及其衍生物激发过程中供电子体,c环是电子受体,尤其N处。有望对今后小檗碱衍生物合成设计提供一定的理论指导。     

聚乙烯的多重弛豫与正电子湮没寿命谱

在143～373K用正电子湮没寿命谱(PALS)方法研究了高密度聚乙烯(HDPE)中的自由体积与温度 的关系.对实验谱分别进行了三寿命成分和四寿命成分分析,并对实验拟合结果作了微分的尝试.发现经这种方 法处理后的结果对温度变化十分灵敏,并且从四寿命分析的微分曲线可以完整地观察到HDPE在该温度区间的 三重α弛豫和表观双玻璃化转变过程,而用三寿命分析的微分曲线将难以解释这些转变.这说明对部分结晶的 聚合物而言,用四寿命拟合比三寿命拟合更符合实际的物理过程;讨论了正电子在HDPE中的湮没机制,证实正 电子在HDPE的结晶区和非晶区都可能形成电子偶素(Ps),而且正电子所处的空间大小对Ps产额有影响;最后 根据PALS实验的结果直接估算了HDPE在不同温度下的热膨胀系数.     

Density Functional Theory Study on Organic Dye Sensitizers Containing Bis-dimethylfluorenyl Amino Benzofuran

运用密度泛函理论和含时密度泛函理论研究了两种含二-二甲基芴氨基苯并呋喃基团的有机染料敏化剂的几何结构、电子结构、极化率和超极化率以及紫外可见谱. 基于理论计算和实验结果的一致性指认了电子吸收谱的特征. 可见区的吸收带都与光诱导电荷转移过程有关,二甲基芴氨基苯并呋喃基团是在光电转换敏化中起主要作用的基团. 通过对两种染料敏化剂的比较,分析了亚乙烯基对几何结构、电子结构和光谱特性影响.     

纳米Fe3 O4 颗粒的正电子湮没谱学研究

测量了磁性纳米Fe₃O₄颗粒的X射线衍射谱(XRD)、正电子湮没寿命谱(PALS)和符合多普勒展宽谱(CDBS),研究了不同压力和退火温度对磁性纳米Fe₃O₄颗粒物相、电子结构、缺陷及电子动量分布等的影响. XRD,PALS,CDBS测量结果表明:纳米Fe₃O₄颗粒的缺陷浓度随压力的增加而增大,但物相和缺陷类型并未发生变化;磁性纳米Fe₃O_{4< 关键词： 正电子 3}O₄')" href="#">Fe₃O₄ 寿命谱 多普勒展宽谱     

含喹啉基团的杯芳烃衍生物的合成及其Zn2+和Cu2+配合物光谱性质的研究

杯[4]芳烃下缘引入荧光基团,合成了一种具有荧光特性的新型杯[4]芳烃衍生物(25,27-二2-甲基喹啉杯[4]芳烃,简称MQBC)。通过红外光谱、元素分析、核磁共振氢谱、质谱等波谱分析确定其结构。研究了MQBC的紫外光谱和荧光光谱,并对其Zn2 和Cu2 配合物的荧光性质进行了分析。MQBC与Zn2 和Cu2 作用主要源于其杯式腔体下缘的氧原子提供孤对电子参与配位,紫外光谱实验发现MQBC与Zn2 作用后,226 nm处的吸收强度减弱,315 nm处吸收强度增强,同时测定了结合常数(K=2 064 L.mol-1)与结合比(n=1),MQBC有用于对微量Zn2 检测的前景。荧光光谱实验发现MQBC存在分子内光诱导电子转移过程(PET),导致其荧光较弱;当其与Zn2 和Cu2 生成配合物后,光诱导电子转移受阻,荧光增强。文章初步探讨了光诱导电子受阻作用机理,研究了Zn2 和Cu2 浓度对荧光强度的影响。     

由杂质谱线强度确定等离子体电子温度

本文给出由氢等离子体中高次电离的碳、氧杂质离子的光谱线强度随时间的变化所确定的等离子体电子温度。对角向箍缩装置等离子体作5-950真空紫外光谱与紫外、可见光谱的诊断表明,在第二半周期的0.5,1.0,1.5,1.8μs时,电子温度分别为17,90,200,260eV。     

低密度聚乙烯光引发交联机理Ⅲ.模型化合物n-C24H50的13C NMR研究

用溶液高分辨¹³C NMR谱首次研究了由二苯甲酮(BP)光引发低密度聚乙烯模型化合物直链烷烃n-C₂₄H₅₀交联所产生的H型交联点的结构特征.现已检测和鉴定了光交联样品中与H型交联点相联系的-CH,α-CH₂和β-CH₂上碳的共振谱线,其数据与H型交联点模型化合物、γ-辐射交联正烷烃和聚乙烯所得到的结果符合得很好.在40.83ppm处出现的一个新峰可指认为H型文联点的次甲碳,其相应的31.57和28.37ppm处的另外两个新峰分别指认为相邻的α-CH₂和β-CH₂上碳的共振.本工作中的定量研究表明:在真空和熔融态条件下莱外光照3-5min的样品中H型交联点的数目据估计为每10000个碳原子8.5~11.0个.     

类锌Au~(49+)离子电子碰撞激发速率系数的研究

利用全相对论扭曲波方法和研究电子碰撞激发过程的计算程序REIE06系统计算了类锌Au~(49+)离子从基态(3s~23p~63d~(10)4s~2)的4s、3d、3p和3s电子激发到4 l(l=p、d、f)和5 l(l=s、p、d、f)的碰撞激发强度,研究了在不同入射电子能量下碰撞强度的变化规律,通过对类锌Au~(49+)离子涉及金激光等离子体M带谱,3d→4f和3d→5f电子碰撞激发速率的计算,分析了等离子体中电子温度对碰撞过程的影响.部分计算结果与其它理论及实验结果进行了比较,取得了很好的一致性.     

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.