冲击高压下硝基甲烷的拉曼光谱及其结构稳定性

在单次冲击压缩实验中,借助新建的瞬态拉曼光谱技术实现了对液态硝基甲烷冲击拉曼光谱的原位观测,来探究该样品分子在冲击波作用下的结构稳定性.实验发现,在10.6 GPa的冲击加载下硝基甲烷的拉曼特征峰仅发生了蓝移和展宽,而在观测波段未发现化学变化产生的迹象.这一结果否定了文献所报道的硝基甲烷在6 GPa~8.5 GPa的单次冲击压力区间内发生了化学反应的推论,同时也证实了在10.6GPa的冲击压力下硝基甲烷分子在约为516 ns的压缩时间内能够保持其结构的稳定.     

冲击高压下硝基甲烷的拉曼光谱及其结构稳定性

在单次冲击压缩实验中,借助新建的瞬态拉曼光谱技术实现了对液态硝基甲烷冲击拉曼光谱的原位观测,来探究该样品分子在冲击波作用下的结构稳定性。实验发现,在10.6GPa的冲击加载下硝基甲烷的拉曼特征峰仅发生了蓝移和展宽,而在观测波段未发现化学变化产生的迹象。这一结果否定了文献所报道的硝基甲烷在6GPa~8.5GPa的单次冲击压力区间内发生了化学反应的推论,同时也证实了在10.6GPa的冲击压力下硝基甲烷分子在约为516ns的压缩时间内能够保持其结构的稳定。     

液相硝基甲烷分子振动特性的相干反斯托克斯拉曼散射光谱

构建时间分辨相干反斯托克斯拉曼散射（CARS）光谱系统,从微观层次研究硝基甲烷的分子相干振动动力学特性.实验中采用超连续白光作为斯托克斯光,通过调整斯托克斯光的时间延迟,得到不同振动模式的CARS光谱.通过对振动弛豫曲线的拟合,获得硝基甲烷分子不同振动模式的振动失相时间.结果表明C–H键伸缩振动比C–N键伸缩振动更容易受热声子的影响.在热加载下,硝基甲烷分子的C–H键有望首先被激发并引起初始化学反应.     

低Z流体的单次冲击波压缩极限

低Z流体的单次冲击波压缩极限是判断各种研究高压物态方程理论和实验正确与否的重要参数。维里定律和Hugoniot方程表明,单次冲击波压缩率是由各种因素的相对重要度决定的,包括平均势能、平均动能、内部自由度的激发度和逆幂函数型势能曲线的幂指数。如果幂指数大于2,相互作用势能使流体变得比理想气体更难压缩,否则流体就比理想气体更容易压缩。内部自由度的激发总是让流体变得更容易压缩。在各种不同因素起主导作用的压强段,低Z流体的单次冲击波压缩极限不同。用一个简单的单次冲击波压缩极限的表达式解释了低Z流体在离解区域和电离区域的行为。     

Liquid xenon study under shock and quasi-isentropic compression

Abstract

The shock adiabat for liquid xenon in the density range of 5.2–7.9 g/cm³ and pressure range of 8–70 GPa was investigated. The brightness temperature of a shock wave front from 5000 K to ?15,000 K, as well as the electrical conductivity behind the front from 4·10³ to 1.2·10⁵ 1/Ohm m, were measured. X-ray technique was used to measure quasi-isentropic compression of liquid xenon up to ～13 g/cm³.

The equations of state for liquid and solid phases of xenon were found. Anomalous behavior of xenon at p=8.37 g/cm³ was revealed, that is due to a structural transition.     

Computing Raman and infrared wavenumbers of nanostructures: application to silicon nanowires

The characterization of nanostructures with spectroscopic methods is a fundamental tool in nanoscience. For novel nanostructures, the interpretation of spectral features is a challenging task. To address this issue, we present the “Symmetry‐Filtered Molecular Dynamics (SFMD)” method to calculate Raman and infrared wavenumbers from molecular dynamics (MD) simulations, employing only the symmetry of the atomic structure. Explicit and expensive calculations of the electric polarizability or the dipole moment are not required. Therefore, our method can be easily used with any standard MD software. On the basis of the density functional tight‐binding method for the MD simulations, we apply our method to bulk silicon and small‐diameter hydrogen‐passivated silicon nanowires. For bulk silicon, we study the wavenumber shift of the Raman peak with temperature and obtain results that are in good agreement with experiments. We further show that thermal lattice expansion is a minor effect (22%) and that temperature‐driven anharmonic effects (78%) are the main contributions to that wavenumber shift. By analyzing the bond lengths of different silicon nanowires, we found that surface stress manifests as a 0.37% shortening of bonds only in the outermost silicon layer. We further analyzed the diameter‐dependent wavenumber shift of a Raman peak in silicon nanowires. We found that the main contribution to the wavenumber shift comes from the phonon confinement effect and surface stress leads to an additional shift of 9–22%. Our results indicate that our method is able to produce quantitative results that can be compared with experiments. We propose our method to be used for the understanding of Raman and infrared spectra of novel bulk and nanostructures. Copyright © 2012 John Wiley & Sons, Ltd.     

多波长消荧光拉曼光谱仪的研制及应用研究

拉曼光谱技术作为探究分子、晶体及其结构特征的有力手段,具有快速、无损、样品用量小、无需前处理且适应性强等优点,已被广泛应用于食品安全、石油化工等领域。但在拉曼光谱应用中,常常受到荧光背景干扰,导致拉曼信号降低,严重的情况下拉曼信号甚至会淹没在荧光背景中。为解决拉曼技术在实际应用中荧光背景干扰的问题,从仪器角度出发,采用二色镜对多波长拉曼光谱进行光路耦合设计,研制了近红外拉曼光谱与移频差分拉曼复合一体的多波长消荧光拉曼光谱检测系统,其中近红外拉曼光谱采用1 064 nm激光光源设计,移频差分拉曼光谱选取784.5和785.5 nm两组激光光源进行时分复用,在移频差分拉曼光谱检测的同时,亦可获得两组单波长拉曼光谱数据。通过对比同步测试和分时逐次测试的强度及峰位稳定性,验证了多波长消荧光拉曼光谱仪的同步测试性能;选取了多种荧光背景强弱不同的样品,进行了单波长拉曼、近红外拉曼及移频差分拉曼光谱的对比分析。针对丙酮、乙腈等荧光背景较弱的样品,可采用单波长拉曼光谱对样品进行定量及定性分析;针对食用油、红色塑胶微粒等荧光背景与拉曼信号强度相当的样品,可采用近红外拉曼光谱对样品进行定量及定性分析;针对红酒、棕色塑胶微粒等荧光背景较强的样品,需结合近红外拉曼光谱和差分拉曼光谱对样品进行定性分析。研究表明：通过多波长消荧光拉曼光谱检测系统的研制,在常规单波长拉曼光谱技术的基础上,将两种抑制荧光干扰技术有机结合,有效扩充了应用领域及样品检测范围。     

基于激光拉曼光谱的水面油膜厚度测量方法研究

为了实现水体表面油膜厚度的快速非接触检测,基于激光拉曼光谱检测技术,搭建了水体表面油膜厚度拉曼光谱检测系统。以532 nm激光作为激发光源,以常见的柴油和汽油为例研究了不同油品的拉曼光谱特性,研究结果表明,油膜拉曼光谱响应特性与油品密切相关,相同油膜厚度情况下不同油品的拉曼光谱曲线有明显的差异,97#汽油在1 651 cm-1光谱强度要高于90#汽油。随着油膜厚度的增加,柴油316和1 451 cm-1光谱强度和汽油1 651 cm-1拉曼位移光谱强度增加,油拉曼光谱信号变强;根据油水界面拉曼光谱特征,设计了油膜厚度计算因子,实验证明随着油膜厚度增加,油膜厚度计算因子r_film呈下降趋势。可以将油膜厚度计算因子作为水体表面油膜厚度测量的一种依据。     

RNA碱基的太赫兹光谱和拉曼光谱特征研究

应用傅里叶红外光谱仪和激光拉曼光谱仪测试了RNA碱基在太赫兹波段(1～10 THz)的红外和拉曼光谱,同时结合Guassian09软件和周期性边界条件下基于能量的分块方法(PBC—GEBF),分析了RNA碱基晶体的红外和拉曼光谱特征,得到了所有特征峰位置及其对应的振动模式,且计算光谱与测试光谱一致吻合,表明碱基粉末样品为无定形晶体结构。通过对红外光谱的分析可知,在太赫兹波段,腺嘌呤和鸟嘌呤都有6个红外活性振动模式,胞嘧啶和尿嘧啶分别为6个和3个红外活性振动模式,与实验结果相比,除了鸟嘌呤6.35 THz处的弱吸收峰没能重现,4.83和5.39 THz处的吸收峰简并;胞嘧啶4.3和4.79 THz处吸收峰简并;尿嘧啶3.32和3.82 THz处的吸收峰简并外,其他吸收峰的位置和强度均被准确地模拟重现。通过对拉曼光谱的分析可知,理论和实验光谱基本一致,除了尿嘧啶3.52和4.48 THz处特征峰简并;鸟嘌呤7.26和8.03 THz,3.57,4.02,4.49,4.89和5.98 THz处特征峰简并外,其他特征峰的位置和强度均被准确的模拟重现。通过对特征峰的分析和辨认,可知在1～10 THz,RNA碱基的振动模式均来源于晶格内分子的集体振动,分子间的氢键和弱相互作用力对振动模式的贡献很大,进一步分析可知,在1～5.5 THz,其振动模式来自所有原子参与的集体振动,在5.5～10 THz,振动模式来自于部分原子参与的集体振动。此项研究对揭示RNA碱基在构成生物大分子结构、生物大分子鉴定以及太赫兹波段光谱的形成机制等方面,具有重要的理论和实际参考价值。     

The fluorescence interference in Raman spectrum of raw coals and its application for evaluating coal property and combustion characteristics

Fluorescence interference in Raman spectrum is a big barrier for rapid and precise analysis of coal structures by Raman spectroscopy. Dealing with fluorescence interference suitably is one of the key tasks before efficient application of Raman spectroscopy in coal assessment. In this study, Raman spectra and coal combustion characteristics of 32 kinds of Chinese coals were respectively obtained in a micro-Raman spectrometer and Thermal Gravimetric Analyzer. The degree of fluorescence interference in Raman spectrum was firstly defined and quantified as the drift coefficient α using a simple method without curve-fitting the spectrum. The correlations between the degree of fluorescence interference and coal property, coal combustion characteristics were set up and multivariable analysis was done. The results indicate that the degree of fluorescence interference is well related to the coal structures, and it is synthetically determined by volatile, moisture and ash content in coal. With the increase of volatile, moisture content in coal, the fluorescence interference increases continuously, and it can be reduced but not eliminated by drying the moisture in coals. Significant mathematical relations between the drift coefficient α and volatile, moisture content, coal combustion characteristic temperatures have been found. Coal with more evident fluorescence interference in Raman spectrum usually has lower degree of coalification, more polar functional groups, and burns at a lower temperature. The drift coefficient α can act as an efficient probe for coal property and coal combustion characteristics. This study provided a new and simple approach for evaluating coal property and coal combustion characteristics by fluorescence interference in Raman spectrum.     

Fourier Transform Infrared and Raman Spectra of 4-Vinylpyridine and its Transition Metal(II) Tetracyanonickelate Complexes

Abstract

Infrared and Raman spectra (4000-200 cm^?1) were recorded for 4-vinylpyridine and vibrational assignments made for fundamental modes on the basis of frequency shifts of the coordinated ligand, of the group vibrational concept and comparison with the assignments for related molecules. the infrared spectra of M(4-vinylpyridine)₂Ni(CN)₄ (M=Mn, Cd, Fe, Co, Ni or Cu) are reported.     

Influence of carbon‐coated iron nanoparticles on the Raman spectrum of liquid ethanol

Raman spectroscopy is applied to study the interactions between carbon‐coated iron nanoparticles and ethanol. The spectra reveal changes in the vibrational structure of ethanol, despite dispersion of only a very small amount of nanoparticles. The hydrogen bonding network of ethanol is significantly affected in the presence of the particles. This is revealed by frequency shifts throughout the spectrum as well as the modification of the OH stretching band of the alcohol. The carbon shell of the nanoparticles does not exhibit polar groups, and hence the non‐polar interactions in the system are strengthened and the hydrogen bonding is weakened. Copyright © 2015 John Wiley & Sons, Ltd.     

电场条件下氧化锌结晶特性及极化产物的拉曼光谱分析

开展高压电场调控纳米材料结构形貌和性能研究在功能材料领域具有重要的理论和实际意义.本文在高压电场条件下合成了氧化锌纳米粉体,并对粉末试片进行了后期电场极化处理,研究了电场对氧化锌的结构形貌、点缺陷、拉曼光谱的影响.以X射线衍射仪(XRD)、扫描电镜(SEM)和拉曼光谱仪对产物的结构形貌、拉曼位移、缺陷分布等进行了表征.结果表明,高压电场条件下氧化锌的完全晶化时间和温度比未施加电场时明显延长和升高,直流电场能够显著促进前驱物中氧化锌的形核,并降低晶化速度.不同电场强度下氧化锌具有不同的显微形貌.纳米氧化锌粉末试片在直流电场中极化后,其阴极面和阳极面的拉曼光谱表现出明显的差异.有明显漏电电流的情况下,阳极面在1050 cm~(–1)处的二级光学声子模A_1(LO)的强度显著提高,且拉曼强度I_1=438 cm~(–1)和I_2=1050 cm~(–1)的比值与极化电场的场强呈线性关系.当调转试片正反面进行二次极化时,原来在阳极面尖锐的1050 cm~(–1)峰经过阴极极化而消失.阳极面1050 cm~(–1)拉曼峰的锐化与氧化锌晶粒内的缺陷重新分布和双肖脱基势垒有关.     

液氘状态方程实验数据测量

在神光Ⅱ高功率激光装置上建立了液氘状态方程实验研究系统, 在80 min内实现控温范围12–300 K可调、控温精度±0.03 K、机械震动 ≤20 μm的实验控制精度; 通过镀膜窗口质量筛选和靶体清洁工作解决了低温下窗口材料残余反射率高的难题, 获得了信噪比较好的实验图像; 利用神光II第九路输出3ω (351 nm)、3 ns、1000 J的能力, 采用阻抗匹配方法, 配合任意反射面速度干涉仪诊断系统, 在国内首次获得液氘在约60 GPa压力下的冲击绝热线实验数据, 数据与国外同压力区间数据符合较好, 为下阶段约100 GPa压力范围液氘状态方程的实验研究奠定了基础.     

1,4-苯二硫醇的表面增强拉曼光谱和激发态的密度泛函理论研究

利用密度泛函理论(density functional theory,DFT)在B3LYP/6-311+g(d)(C,H,S)和Lanl2dz(Ag、Au)基组下对1,4-苯二硫醇分子及其复合物进行了结构优化和频率计算,得到了分子及其复合物稳定的化学构型和拉曼光谱。优化后的1,4-苯二硫醇分子的S—H键和苯环所在平面夹角为20.2°,分子非平面结构。模拟了金银团簇在苯硫醇分子表面的吸附行为,得到了金团簇和银团簇在分子表面的吸附方式,即,金团簇以接近平行的方向吸附于苯硫酚分子的表面而银团簇则以几乎垂直的方向吸附于分子表面。此外,还分析了静态极化率数值变化和自然键轨道(natural bond orbital,NBO)布局分析得到的电荷分布对拉曼光谱的强度变化的影响。复合物1,4-BDT-Au2,1,4-BDT-Ag2和三明治结构的Ag2-1,4-BDT-Au2拉曼光谱谱峰强度与静态极化率数值变化有很好的吻合。采用含时密度泛函理论(time dependent density functional theory,TDDFT)对Ag2-1,4-BDT-Au2复合物进行了激发态的分析计算,通过模拟吸收光谱和计算轨道跃迁单激发态,分析计算了三明治结构的电荷转移激发态,利用可视化的电荷转移,研究了表面增强拉曼(surface enhanced Raman scattering,SERS)化学增强机理。     

Nonlinear scaling and its application to ferromagnetic systems

Making use of renormalization-group ideas, a scaling equation of state applicable to ferromagnetic systems and involving the nonlinear scaling variables =ε/t and =h/t, instead of the usual linear scaling variables ε=(T-T_c)/Tc = t-1 and h=H (ordering field), has been derived. The magnetic equation of state so obtained is then generalized to take into account the effect of nonlinear relevant and irrelevant scaling fields. To facilitate a comparison with experiments, the analytic (non-analytic) corrections to the dominant singular behaviour of spontaneous magnetization (order parameter) M(T, 0), ‘zero-field’ susceptibility χ(T, 0), and specific heat in zero field that the nonlinear relevant (irrelevant) scaling fields give rise to are explicitly calculated up to third order in Due consideration is also given to the modifications in the Arrott-Noakes form of the scaling equation of state and the Kouvel-Fisher definition of the effective susceptibility exponent brought about by these scaling fields. A detailed analysis of the M(T, 0) and χ(T, 0) data for crystalline and amorphous ferromagnets in terms of the theoretical expressions derived in this work reveals that i) in conformity with the theoretical predictions, the “;non-analytic”; corrections to the singular behaviour dominate over the “;analytic”; ones for temperatures in the immediate vicinity of the critical point Tc, whereas reverse is the case for temperatures far away from Tc and (ii) the expression for χ(T, 0), based on the nonlinear scaling arguments, which includes the leading “;analytic”; correction, reproduces closely the observed variation of χ with T over a wide range of temperatures T_c ≤ T ≤ 1.5T_c (in some cases, up to 3T_c) for both ordered as well as quench-disordered ferromagnets.     

稀土化合物Raman谱中荧光带的辨认

研究了三价稀土氧化物及退火结晶褐钇铌矿和褐铈铌矿在４８８０和５１４５ｎｍ激光激发下所得Ｒａｍａｎ光谱中的荧光带。结果表明,在这两种激光线激发下,Ｓｍ３＋、Ｅｕ３＋和Ｅｒ３＋的荧光对稀土化合物的Ｒａｍａｎ光谱有很大干扰。提出几种在稀土化合物Ｒａｍａｎ光谱中辨认荧光带的方法。     

氧化锡纳米线的拉曼光谱和光致发光光谱研究

用表面限制剂对水热法生成的前驱物加以限制生长的方法成功制备了氧化锡纳米线结构,TEM和HRTEM的结果表明该纳米线由沿[001]方向生长的氧化锡单晶组成,纳米线直径在5-10纳米、长度100-500纳米。利用拉曼光谱和发光光谱对其生长过程和发光现象进行了详细的研究,结果表明,细长的氧化锡纳米线出现356、515、691 cm-1新的拉曼振动模以及600 nm较强的光致发光。     

Mechanical properties,lattice thermal conductivity,infrared and Raman spectrum of the fullerite C24

Lightweight carbon materials with excellent thermal and mechanical properties have important applications in aerospace industry. In this study, the stability, mechanical properties, lattice thermal conductivity, electronic structure, infrared and Raman spectrum of sp³ hybridized low-density fullerite C₂₄ were investigated according to density functional theory (DFT) calculations. It was found that the fullerite C₂₄ was both thermodynamic and dynamic stable. Quasi-harmonic approximation and Grüneisen parameter calculations clarified why the fullerite C₂₄ had a positive thermal expansion coefficient at low temperature. The fullerite C₂₄ also exhibited excellent mechanical properties. Interestingly, the Vickers hardness of carbon allotropes was found to almost be linear proportional to the density of a carbon material. HSE06 electronic structure calculations showed that it was a semiconductor with direct bandgap of 2.56 eV. Anharmonic lattice dynamic calculations showed that its thermal conductivity was higher than semiconductor silicon. Besides, Raman and infrared active modes as well as the corresponding spectra were presented.