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1.
介绍了一种新的表面和频振动光谱方法: 定量手性检测中的双偏振角方法. 一般来讲表面光谱信号中非手性项贡献最强,而纯界面手性信号要比非手性信号弱两到三个数量级. 因此在和频振动光定量测量和分析界面手性的贡献问题上存在困难. 在和频振动光谱的双偏振角方法中,通过固定入射红外光偏振方向,并同时改变入射可见光和初涉和频信号光的偏振角进行测量. 这样所得到的偏振依赖的和频振动光谱信号能够直接给出界面手性贡献的特征,并 且能够用于准确测量界面的手性和非手性贡献. 对双偏振角方法进行了描述,并且通过S和R手性的柠檬烯空  相似文献   

2.
对四种不同的实验构型下空气/水界面自由O-H键在3700cm~(-1)的和频振动光谱的分析表明,水分子在空气/水界面的取向运动只可能是在平衡位置附近有限角度之内的受限转动。界面水分子的自由O-H键取向距界面法线约33°,而取向分布或运动的宽度不超过15°。这一图像显著地不同于Wei等人(Phys. Rev. Lett.86,4799(2001))只通过单一的SFG实验构型所得出结论,即:空气/水界面的水分子在超快的振动弛豫时间内在很大的角度范围内运动。  相似文献   

3.
对空气/甲醇液体界面的和频振动光谱进行了定量的理论分析.虽然甲醇的红外和Raman光谱中都具有明显的反对称伸缩振动峰,但该光谱峰在界面和频振动光谱中却从未被观测到.利用已知的甲醇液体的红外和Raman光谱对和频振动光谱的键极化模型进行了修正,从而对此实验现象进行了定量的解释.此修正可以广泛地应用于界面和频振动光谱的研究中.  相似文献   

4.
和频振动光谱(SFG-VS)研究中由基团在界面上取向所引起的光谱增强或相消的干涉现象为研究分子在界面上的绝对取向提供了一种直接的测量方法. 这一方法比SFG实验中复杂的相位测量方法更为直接和简单可行. 以在空气/水界面取向已知的对羟基苯腈(PCP)分子的氰基(-CN)基团为相位参考来获得3,5-二甲基对羟基苯腈(35DMHBN)和2,6-二甲基对羟基苯腈(26DMHBN)分子在空气/水界面的取向信息. 通过对这三种分子的水溶液和它们两两混合溶液界面上-CN基团和频振动光谱强度的比较,发现在空气/水界面的3  相似文献   

5.
(SiO2)nO2H4的红外振动光谱的理论研究   总被引:1,自引:0,他引:1  
运用密度泛函理论,在6-31G(d)基组水平上,计算了纳米尺度的(SiO2)nO2H4链状、环状、笼状三种不同构型的红外振动光谱.对准一维的链状和环状结构,红外振动较强峰的频率随着长度的增加单调变化,显示了较强的尺寸依赖性;沿纳米线(环)轴向和垂直于轴向的振动模式,频率对尺寸的依赖关系相反,揭示了纳米材料的振动性质的各向异性.笼状结构由于构型的复杂性而使得其不具备准一维的特性,同时结构的对称性降低,红外振动模式数目增加.三种构型中二元环和硅羟基的振动以及笼状构型中硅氧四面体骨架的振动与实验上所观测到的振动峰相吻合.红外光谱方面的理论计算结果对实验合成的SiO2纳米材料的表征具有指导意义.  相似文献   

6.
许多物理、化学和生物过程发生于气液界面,且受到局域微观结构的深远影响.不同于液体的体相,分子取向是界面处微观结构突出的不对称特征之一.本文综述了电子碰撞时间延迟质谱方法和近期取得的进展.利用这个崭新的方法,不仅可以侦测得到利用小角度X射线或中子散射以及振动和频光谱方法获得的界面微观结构,同时也提供了一种研究气液界面处电子驱动化学反应的实验方案.  相似文献   

7.
许多物理、化学和生物过程发生于气液界面,且受到局域微观结构的深远影响. 不同于液体的体相,分子取向是界面处微观结构突出的不对称特征之一. 本文综述了电子碰撞时间延迟质谱方法和近期取得的进展. 利用这个崭新的方法,不仅可以侦测得到利用小角度X射线或中子散射以及振动和频光谱方法获得的界面微观结构,同时也提供了一种研究气液界面处电子驱动化学反应的实验方案.  相似文献   

8.
精确表征界面蛋白质结构与动力学行为是理解生物大分子功能及其与界面相互作用机制的核心.而其关键在于发展同时具有足够结构与时间分辨度的技术来捕捉界面蛋白质的动态结构变化.本文利用本小组最近发展的飞秒和频振动光谱系统来实时研究蛋白质跨膜传输过程.该系统实现目前文献报导中最快的和频光谱采谱速度.通过实时监控WALP23与DMPG双层膜作用过程中酰胺I和酰胺A的和频信号,发现WALP23最初以无规则卷曲结构吸附在凝胶相的DPMG双层膜表面.DMPG膜表面上WALP23的吸附,会导致膜表面电荷发生反转,从而改变膜界面水分子的取向.通过加热使DMPG由凝胶相转变为流动相后,WALP23以N端插入的方式实现跨膜过程.在跨膜过程中,WALP23结构由无规则卷曲转变为α-螺旋/回环混合结构,最后形成纯α-螺旋结构,同时引起DMPG膜的去水合作用.此系统可直接应用到其他界面快过程的表征工作,将有助于深入理解各种界面现象的本质.  相似文献   

9.
研究了空气/二甲亚砜界面C?H伸缩振动的自由诱导衰减的相干振动动力学和亚波数高分辨宽带和频振动光谱.对于特定分子体系,频率域光谱测量和时间域动力学测量原则上应获得相同的信息.但对具有耦合或者重叠在一起的若干振动模式的分子体系,通过时域或者频域测量以获取光谱和动力学信息细节均非易事.对于振动光谱并非过于复杂的空气/二甲亚砜界面,基于亚波数高分辨宽带和频振动光谱的频域测量较超快时域测量更有益于获取界面结构和相干动力学定量信  相似文献   

10.
梓醇是一种具有特殊药理活性的环烯醚萜苷类化合物.采用密度泛函(DFT)B3LYP/6-311G**方法对梓醇分子的几何构型进行全优化,得到其儿何构型参数,进一步计算得到梓醇的红外振动光谱,振动频率校正因子为0.96.对计算得到的振动频率进行归属和解析并与实验测定得纠的梓醇IR光谱特征峰比较,发现理论计算出的IR光谱与实验测定IR特征峰位具有很好的一致性,说明所采用的DFT方法能够用于梓醇分子几何构型的优化,预测难以得到标准对照品的环烯醚萜苷类化合物的IR光谱数据.  相似文献   

11.
Infrared (IR) spectroscopy has evolved into a powerful analytical technique to probe molecular and lattice vibrations, low-energy electronic excitations and correlations, and related collective surface plasmon, phonon, or other polaritonic resonances. In combination with scanning probe microscopy, near-field infrared nano-spectroscopy and -imaging techniques have recently emerged as a frontier in imaging science, enabling the study of complex heterogeneous materials with simultaneous nanoscale spatial resolution and chemical and quantum state spectroscopic specificity. Here, we describe synchrotron infrared nano-spectroscopy (SINS), which takes advantage of the low-noise, broadband, high spectral irradiance, and coherence of synchrotron infrared radiation for near-field infrared measurements across the mid- to far-infrared with nanometer spatial resolution. This powerful combination provides a qualitatively new form of broadband spatio-spectral analysis of nanoscale, mesoscale, and surface phenomena that were previously difficult to study with IR techniques, or even any form of micro-spectroscopy in general. We review the development of SINS, describe its technical implementations, and highlight selected examples representative of the rapidly growing range of applications in physics, chemistry, biology, materials science, geology, and atmospheric and space sciences.  相似文献   

12.
基于透明导电材料氧化铟锡(ITO)、高透光的聚对苯二甲酸乙二醇酯(PET),设计并实现了光学透明超宽带雷达与红外兼容隐身的复合超表面。该结构由两个专门设计的光学透明超表面组成,由内到外依次为雷达吸波层、红外低发射层。通过调节谐振器尺寸和ITO的方阻实现了微波段8.0~32.0 GHz频带内吸收率高于90%的宽带吸波。利用高ITO占空比的容性频率选择表面,实现了微波段高透过率与红外波段低发射率,并进一步研究了其红外辐射特性。该结构具备较好的超宽频雷达吸波性能、低红外发射率与光学透明特性。  相似文献   

13.
Abstract

A number of far infrared absorption bands are found in molecular and hydrogen-bonded crystals when there are several formula units in the primitive cell. They are very sensitive to the crystal structure and constitute a convenient probe for looking at small changes in the structure, especially at low temperatures where there is a lack of X-Ray data. As well known examples, the case of LTT (Lithium Thallium Tartrate) where the absorption band observed at 21 cm?1 at room temperature softens down to 8 cm?1 at the Curie temperature (Tc = 12 K), and LiNH4SO4 which has a phase transition at 26 K, will be considered.

It is less known that some ferroelectric crystals can be studied as very thick single crystal plates (thickness t up to 10 mm) at 4 K, and they show in some cases a far IR transmission that is much higher than expected from the study of thin plates (i.e. t = 20 μm). In fact the transmission does not decrease very much when thickness is higher than some specific value t 0/2. The crystal is not homogeneous at 4 K. A model with a far IR absorbing surface layer (thickness t 0/2) and a transparent bulk is a good first approximation.

At some temperature T 0 located between liquid helium and liquid nitrogen temperatures, the center of the bulk undergoes a phase transition from the absorbing phase into the transparent one. When temperature is still lowered, the transparent phase is extended towards the surface with an incommensurate phase between the surface and the bulk.  相似文献   

14.
Single-shot thresholds of surface ablation of aluminum and silicon via spallative ablation by infrared (IR) and visible ultrashort laser pulses of variable width τlas (0.2–12 ps) have been measured by optical microscopy. For increasing laser pulse width τlas < 3 ps, a drastic (threefold) drop of the ablation threshold of aluminum has been observed for visible pulses compared to an almost negligible threshold variation for IR pulses. In contrast, the ablation threshold in silicon increases threefold with increasing τlas for IR pulses, while the corresponding thresholds for visible pulses remained almost constant. In aluminum, such a width-dependent decrease in ablation thresholds has been related to strongly diminished temperature gradients for pulse widths exceeding the characteristic electron-phonon thermalization time. In silicon, the observed increase in ablation thresholds has been ascribed to two-photon IR excitation, while in the visible range linear absorption of the material results in almost constant thresholds.  相似文献   

15.
实验测量了1,1''-联萘-2,2''-二胺(BINAM)的红外吸收光谱、可见光激发普通拉曼光谱、紫外共振拉曼光谱.用电子密度泛函方法计算了BINAM的基态几何构型、振动频率、普通拉曼和近共振拉曼强度.通过实验和理论计算对比,对所得红外和拉曼提出了详细的指认,并且分析了各振动模式的特征.BINAM的紫外共振拉曼光谱与普通拉曼光谱相比较,发现有若干拉曼谱带出现了选择性共振增强.基于共振拉曼强度分析,讨论了BINAM可能的激发态几何结构的变形.  相似文献   

16.
Gold, rhodium and their coadsorbed layers were prepared on titanate nanowires and nanotubes and characterized by X-ray photoelectron spectroscopy (XPS), low energy ion scattering spectroscopy (LEIS), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). On titanate nanowire and tube supports the gold 4f7/2 XP emission appeared after reduction at 83.7 eV and 85.6 eV indicating two different sizes or chemical environments of gold nanoclusters. The titanate nanostructures stabilize the nearly atomically dispersed state of gold (85.6 eV peaks in XPS). Small clusters also developed in rhodium containing samples besides the pure metallic state. Upon CO adsorption on Rh/titanate nanostructures the IR stretching frequencies characteristic of twin form were dominant, whereas bimetallic nanosystems featured a pronounced linear stretching vibration. By performing careful XPS, LEIS and SEM experiments, it was found that, for appropriate Au and Rh coverage, the Au almost completely covers the Rh nanoparticles. CO adsorbed on this surface may induce the surface reconstruction.  相似文献   

17.
Images of a target in a specific spectral band in general show no correlation with images of the same target in a different spectral band. Hence in a joint transform correlator (JTC) architecture, if the reference and input target are the images captured through a visible (e.g., charge-coupled device or CCD camera) and infrared (IR) detector, autocorrelation peaks are not obtained. This drawback has been overcome in this paper by the use of a CCD–IR fused image as the reference image. Daubechies wavelet transform, which produces the least root-mean-square (RMS) error in the fusion process in comparison to other wavelets, has been used for the purpose. A comparative analysis of the proposed idea has been carried out for the classical JTC (CJTC), binary JTC (BJTC) and differential binary JTC (DBJTC) algorithms. Since the DBJTC removes the dc completely and produces sharp correlation peaks compared to the other techniques, computer simulation and experimental results are shown for the proposed idea using DBJTC. The same fused reference image has also been used to identify multiple targets in a scene using DBJTC. Performance measures like correlation peak intensity (CPI), dc/ac and peak correlation energy (PCE) have been calculated as metrics of goodness for the proposed scheme.  相似文献   

18.
We propose the application of nitroanisole as a detector for middle infrared (mid-IR) interferometry or holography. The present experiment utilizes the liquid form of nitroanisole, which has a thermal lens effect, i.e. a temperature dependent refractive index. Since the nitroanisole absorbs IR radiation as heat, it is possible to estimate the IR intensity distribution on the nitroanisole from the diffraction pattern made by visible laser light that is transmitted through the nitroanisole. In this study, the time resolution and the diffraction efficiency of the nitroanisole was measured under various conditions. The experimental results show that the nitroanisole has a time resolution as high as that of a standard video camera, as well as a high diffraction efficiency and the spatial resolution equivalent to that of a conventional IR camera. Furthermore, we confirmed that the phase shift in mid-IR region can be estimated by analyzing the change in the visible diffraction pattern.  相似文献   

19.
《Applied Surface Science》2005,239(3-4):262-267
Metal-based transparent heat mirror for ultraviolet curing applications was designed in terms of induced transmission principle, good ultraviolet transparency and high infrared ray (IR) reflection properties can be obtained by the means of optimal layers design. After a comprehensive analysis to materials properties, TiO2/Ag/TiO2 nano-multilayers with a Ultraviolet (UV) transmission of 81% (at 365 nm) and an IR reflectivity of 90% (at 1600 nm) were designed and prepared by conventional evaporation. The multilayers exhibit a sharp interface between dielectric and metal layers by spectroscopic ellipsometry analysis. The experiment results prove that critical thickness of metal layer determined in light of admittance match and skin effect has no applicable meaning in long-wavelength UV region. Dependence of transmittance in near UV spectra on the thickness of metal layer is less sensitive than that in near IR. This transparent heat mirror can be applied in the “windows” of ultraviolet curing system for heat insulation.  相似文献   

20.
Dehydroxylated silica exhibits two well-defined infrared bands at 888 and 907 cm−1 previously assigned to a highly reactive strained surface defect. Comparisons of the spectra of dehydroxylated silica to frequencies and intensities calculated using molecular orbital (MO) calculations and to spectra obtained for cyclodisiloxanes suggest that the strained surface defect consists of an edge-shared silicate tetrahedral ring. Changes in vibrational frequencies and peak intensities with 18O labeling for both the surface defect and the cyclodisiloxanes are consistent with those expected for ring vibrational modes. The IR bands associated with the strained edge-shared ring disappear when either the surface defects or the cyclodisiloxanes react with water. Reactions of the surface defect can be used to study how strain enhances the reactivity of Si-O-Si bonds for modeling phenomena such as stress corrosion cracking.  相似文献   

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