拉曼光谱退偏度测量实验的设计及其应用的研究

本文根据拉曼光谱的理论,利用LRS-Ⅲ型激光拉曼光谱仪设计了拉曼光谱退偏度测量的实验,对四氯化碳CCl4退偏度测量的结果与理论计算值吻合;并以苯和环己烷为例,提出了根据拉曼光谱退偏度的测量判断未知物质的分子结构的方法及其在温度、压力等物理条件变化时动态研究分子结构和机理中的应用.     

1,2,4-三唑-3-羧酸溶液的拉曼光谱研究

本文实验测量了1,2,4-三唑-3-羧酸根(TC^-阴离子)及其环去质子化衍生物(dp-TC^2-二价阴离子)在水溶液中的拉曼光谱,并采用MN15泛函和PCM溶剂模型计算了其几何结构、振动频率和拉曼强度. 基于计算光谱和氘化位移的测量,对dp-TC^2-的拉曼光谱做了清楚的光谱标识. 本文还系统研究了TC^-阴离子的各种质子互变异构体,发现2H互变异构体比其他互变异构体更稳定,并且TC^-溶液的实验拉曼光谱与单体2H互变异构体的计算光谱也基本一致. 与计算光谱相比,实验观测到的谱带分裂可能来自于TC^-的氢键结合二聚体的影响.     

拉曼光谱偏振特性的研究

在研究拉曼光谱偏振特性的基础上，计算出四氯化碳(CCl4)样品各简正振动模式的退偏度，设计了测量拉曼光谱退偏度的实验方案，并得到理论和实验相吻合的结果。     

CH4分子ν1模拉曼诱导克尔效应谱与受激拉曼光声光谱峰形的比较

以气相甲烷分子ν₁模Q支的拉曼光谱为例，采用拉曼诱导克尔效应谱(RIKES)进行峰形测量，并将其与同时测量的受激拉曼光声光谱(PARS)的峰形进行了比较.结果表明，在pump光和Stokes光均为线偏振的情况下，两者存在着差异；在拉曼共振峰的低频端，RIKES谱强度略高；而高频端则恰好相反.从信号产生机制出发，对此进行了合理解释. 关键词： 拉曼诱导克尔效应谱 受激拉曼光声光谱 峰形     

苯的激光拉曼光谱研究

采用激光拉曼光谱技术获得了苯的振动拉曼光谱,结合群论分析、退偏度测量和相关文献对其中8条拉曼谱线进行了分析.1550～1650cm-1区间内的两条谱线是由于费米共振而形成的.     

CCl4的激光拉曼光谱研究

研究了4条CCl4斯托克斯激光拉曼光谱,通过对CCl4分子结构及振动模式对称性的分析,设计了一套测量拉曼光谱退偏度的实验方案,将实验结果和理论值进行了比较.     

饮用水激光拉曼光谱的比较与分析

为了对我国目前饮用水的质量进行有效检测,对市面上几种常用品牌的饮用水以及实验室提供的蒸馏水等样品做了测量和计算。运用激光拉曼光谱的分析方法,测量了它们的激光拉曼光谱。同时,通过测量计算了样品在对称伸缩振动处拉曼谱的退偏度。结果表明,在水样品的对称伸缩振动处,其拉曼谱的相对强度大小和退偏度的大小有着相同的规律。对结果进行比较和分析后得出了如下结论：可以从拉曼光谱特征峰相对强度的大小和同一特征峰下退偏度的大小两方面来判断饮用水中矿物质含量的相对多少。为鉴定饮用水的质量提供了新的有效途径。     

拉曼光谱退偏度实验的设计与研究

为了研究拉曼光谱偏振特性,设计了5种测量拉曼光谱退偏度的实验方案,得到实验和理论相吻合的结果,比较分析了不同实验方案的区别。     

四氢呋喃（THF）非共振拉曼光谱中反对称散射的贡献

研究了四氢呋喃（ＴＨＦ）非共振拉曼光谱中反对称散射的贡献。在测量ＴＨＦ的非共振拉曼带的退偏比时发现，准转动式环折迭振动带及其组合带υ１６和υ１７虽是全对称振型，但其退偏比ρ约０．７５，远大于其它普通全对称振动带的退偏比。从时间反演对称性和空间对称性分析证明，反对称极化率张量不为零，进一步估计其大小比对称部分小一个量级（或同量级）。反对称散射的重要贡献是υ１６、υ１７振动带大退偏比的重要原因。     

共振拉曼效应和电子-声子耦合对线性多烯分子共振拉曼光谱的影响

线性多烯分子具有高强度且信息丰富的共振拉曼光谱,在生物学、光电材料和医学等方面都有一定应用。而含有共轭双键的短链β胡萝卜素分子是多烯分子中极具有代表性的分子。在激发光作用下π电子与CC键振动相互作用影响着吸收光谱和拉曼光谱,而共振拉曼效应和电子-声子耦合影响着共振拉曼光谱的强度、频率和线型。测量了β胡罗卜素分子在二氯乙烷中283～223 K温度范围内的紫外-可见吸收和共振拉曼光谱。研究了共振效应和电子-声子耦合对吸收光谱和拉曼光谱的变化所起的作用。获得随着温度的降低,黄昆因子减小,表明CC键的振动减弱,分子体系能量减小,吸收峰红移;随着温度的降低,分子有序性提高,电子-声子耦合强度增加,增强了电子能隙对CC键振动的调制作用,拉曼模频率向低波数方向移动,即拉曼光谱红移;同时,经过计算发现随着温度的降低,β胡萝卜素分子C-C和C═C的拉曼散射截面增加,线宽变窄,倍频与基频强度比增加。对比和分析了共振效应和电子-声子耦合作用对拉曼光谱的拉曼散射截面、线宽和倍频与基频强度比的影响。虽然共振效应和电子-声子耦合作用在不同温度下对拉曼光谱都有一定影响,但研究发现不同温度下共振效应对拉曼光谱的影响要大于电子-声子耦合,且电子-声子耦合对谐波的影响更小。这是由于随着温度的降低,发生红移的紫外可见吸收光谱,使拉曼光谱中514.5 nm激发光更接近00吸收峰,明显的增强了分子的共振效应,使其拉曼散射截面,线宽,倍频与基频强度比随温度有很大变化。该研究对共振效应和电子-声子耦合的研究为研究温度对胡萝卜素等线性多烯分子性质的影响提供一定实验和理论依据。     

Raman spectrum and cross sections of n-C3F7I. Implications for a large-scale atomic iodine laser

The Raman spectrum of gaseous n-C₃F₇I has been recorded.Raman cross sections, depolarization ratios, and line widths were measured for the four strongest Raman-active modes. Using the measured values for the 280 cm^-1 mode, the stimulated-Raman gain for a large-scale iodine laser was calculated. The results indicate that losses due to stimulated-Raman scattering will be negligible for a fusion-driver iodine laser.     

Laser Raman Spectrum of Triglycine Sulfate

Abstract

The laser Raman spectrum of ferroelectric triglycine sulfate has been determined by the use of an argon ion gas laser. The observed Raman lines are compared with reported assignments in the literature by Taurel¹ and Krishnan², Determination of depolarization ratio of the sulfate line at 980 cm^?1 shows that the Raman band is highly polarizable and the molecular vibration is totally symmetrical v₁.

The role played by the glycine groups in the spontaneous polarization and its reversal can be indirectly confirmed by Raman spectrum of TGS. Interpretation of the Raman spectrum indicates that the SO₄ groups do not have tetrahedral symmetry at roan temperature. Ferroelectric behavior of TGS is attributed to the glycine groups.     

Low-temperature vibrational properties of KGd(WO4)2: (Er, Yb) single crystals studied by Raman spectroscopy

Temperature-dependent polarized Raman spectra of KGd(WO₄)₂: (Er, Yb) single crystals have been analyzed over the 77-292 K temperature range. The A_g and B_g spectra obtained are discussed in terms of factor group analysis. The spectra have been found to reveal the bands related to internal and external vibrations of WO₄²⁻, WOW and WOOW molecular groups. Strong depolarization of the majority of the Raman bands has been observed in the whole temperature range. Some anomalies in the spectral parameters of selected Raman bands below 175 K have been discussed in terms of the local distortion of WO₄²⁻ ions in KGd(WO₄)₂: (Er, Yb) crystals.     

用CARS技术确定拉曼退偏比的一种数据处理新方法

Yuika等人利用偏振CARS技术可以准确地确定分子的拉曼退偏比.其方法是，首先对不同检偏角_d所对应CARS谱峰的频率分布进行数学模拟，然后由所得系数随检偏角φ_d的变化求得使CARS信号中共振项消失的偏振角φ^０_d，最后由消失条件ρ＝-1/(tanθtanφ⁰_d)求出退偏比ρ，θ为产生CARS光的Pump光与Stokes光偏振方向的夹角.本文提出的数据处理方法，即交点法.同Yuika等人处理数据的方法相比，交点法毋需关于谱峰频率分布的知识，做法也更为简便.     

Raman scattering cross section and density measurements of UF6

We have applied laser Raman scattering to the measurement of the density of UF₆ vapor. A linear relation between scattering intensity and density is shown. We have also measured the absolute Raman scattering cross section of the 665 cm^?1 line of UF₆ by the substitution technique and obtained a value of 1.02±0.09×10^?29 cm²/sterad at 488 nm. Measurements of the line position and the depolarization ratio of this line are also reported.     

Raman study of the α-γ phase transition of lithium iodate

The temperature dependence of Raman spectra of α lithium iodate is studied. Frequencies and linewidths vary slightly vs temperature. We observe a progressive depolarization of the 148, 792 (A-type) and 330 cm^-1 (E₁-type) modes. The intensity of the central line increases sharply at the transition.     

Accurate depolarization ratio measurements for all diatomic hydrogen isotopologues

The Raman depolarization ratios for individual Q₁(J”) branch lines of all diatomic hydrogen isotopologues – H₂, HD, D₂, HT, DT, and T₂ – were measured, for all rotational levels with population larger than 1/100 relative to the Boltzmann maximum at room temperature. For these measurements, the experimental setup normally used for the monitoring of the tritiated hydrogen molecules at KArlsruhe TRItium Neutrino experiment was adapted to optimally control the excitation laser power and polarization, and to precisely define the Raman light collection geometry. The measured Raman depolarization values were compared to theoretical values, which are linked to polarizability tensor quantities. For this, the ‘raw data’ were corrected taking into account distinct aspects affecting Raman depolarization data, including (1) excitation polarization impurities; (2) extended Raman excitation volumes; and (3) Raman light collection over finite solid angles. Our corrected depolarization ratios of the hydrogen isotopologues agree with the theoretical values (based on ab initio quantum calculations by R.J. LeRoy, University of Waterloo, Canada) to better than 5% for nearly all of the measured Q₁(J”) lines, with 1σ confidence level. The results demonstrate that reliable, accurate Raman depolarization ratios can be extracted from experimental measurements, which may be substantially distorted by excitation polarization impurities and by geometrical effects. Copyright © 2013 John Wiley & Sons, Ltd.     

Raman scattering cross section and density measurements of UF6

We have applied laser Raman scattering to the measurement of the density of UF₆ vapor. A linear relation between scattering intensity and density is shown. We have also measured the absolute Raman scattering cross section of the 665 cm⁻¹ line of UF₆ by the substitution technique and obtained a value of 1.02±0.09×10⁻²⁹ cm²/sterad at 488 nm. Measurements of the line position and the depolarization ratio of this line are also reported. Work supported by the U. S. Energy Research and Development Administration.     

Evaluation method for Raman depolarization measurements including geometrical effects and polarization aberrations

In this article, we address the notoriously difficult problem to quantitatively link measured Raman depolarization values to theoretical polarizability tensor quantities, since quantum calculations do not incorporate experimental parameters. For this, we introduce a numerical model to calculate, for realistic experimental configurations, effective Raman line strength functions, Φ, which find their way into depolarization ratios, ρ. The model is based on interlinked integrations over the angles in the light collection path and a finite Raman source volume along the excitation laser beam. The model deals also with the conditional aperture parameters, associated with more than one optical component in the light collection path. Finally, we also can take into account polarization aberrations introduced by the sample cell windows. The procedure was fully tested for Raman depolarization spectra of selected hydrogen isotopologues. Distinct aspects affecting Raman depolarization data were validated, namely: (1) excitation polarization impurities; (2) extended Raman excitation volumes; (3) Raman light collection over finite solid angles; and (4) polarization aberrations introduced by optics in the light collection path. The correction of the experimental measurement data for the aforementioned effects resulted in depolarization ratios for the Q₁(J " ) Raman lines of H₂ and T₂, which mostly differed by less than 5% from those obtained by quantum‐calculations. Copyright © 2013 John Wiley & Sons, Ltd.     

密度泛函理论研究黄曲霉素B1的表面增强拉曼散射效应

用密度泛函理论B3LYP方法和6-311G(d,p)/Lanl2DZ优化得到黄曲霉素B₁(AFB₁)分子及其复合物AFB₁-Ag的稳定结构,并计算了复合物的表面增强拉曼光谱和预共振拉曼光谱. 结果表明,AFB₁分子的拉曼光谱很大程度依赖于吸附位点以及入射光的激发波长. 与分子的常规拉曼光谱相比,复合物表面增强拉曼光谱中C=O伸缩振动模的增强因子约为10²～10³复合物的极化率增强而导致的静态化学增强,并分析了振动模式的振动方向与其拉曼强度的关系．选择复合物最大吸收峰附近激发光266和482 nm以及远离共振吸收波长785和1064 nm作为入射光,计算得到不同入射光激发下复合物的预共振拉曼光谱．结果表明其增强因子最大达到10⁴量级,主要是由电荷转移产生的共振增强引起的．