Difference in effect of temperature on absorption and Raman spectra between all-trans-β-carotene and all-trans-retinol

<正>Temperature dependencies(81℃-18℃) of visible absorption and Raman spectra of all-trans-β-carotene and all-trans-retinol extremely diluted in dimethyl sulfoxide are investigated in order to clarify temperature effects on different polyenes.Their absorption spectra are identified to be redshifted with temperature decreasing.Moreover, all-trans-β-carotene is more sensitive to temperature due to the presence of a longer length of conjugated system.The characteristic energy responsible for the conformational changes in all-trans-β-carotene is smaller than that in all-transretinol. Both of the Raman scattering cross sections increase with temperature decreasing.The results are explained with electron-phonon coupling theory and coherent weakly damped electron-lattice vibrations model.     

Stimulated supercontinuum-radiation generation of carbon disulfide by all-trans-β-carotene fluorescence enhancement effect in liquid core optical fibre

We demonstrate stimulated supercontinuum-radiation of carbon disulfide (CS₂) influenced by biological molecules all-trans-β -carotene in liquid core optical fibre (LCOF). By virtue of the broad fluorescence characteristics and large third-order optical nonlinearities of all-{trans}-β-carotene,the high-order Stokes lines of stimulated Raman scattering (SRS) and the multi-order Stokes lines of stimulated Brillouin scattering (SBS) excitated by SRS are observed at low input-laser energies. The results indicate that the fluorescence not only enhances the SRS, but also the SBS. These Stokes lines generate the SRS--SBS supercontinuum radiation (RBSR). A flat-amplitude bandwidth of 110 nm from 515nm to 625nm is observed when a frequency-doubled Nd:YAG laser at 532nm with an energy of 0.86mJ is used. This result is expected to be useful for the multi-wavelength fibre laser.     

Influence of the ordered structure of short-chain polymer molecule all-trans-β-carotene on Raman scattering cross section in liquid

We measured the resonant Raman spectra of all-trans-β-carotene in solvents with different densities and concentrations at different temperatures.The results demonstrated that the Raman scattering cross section(RSCS) of short-chain polymer all-trans-β-carotene is extremely high in liquid.Resonance and strong coherent weakly damped CC bond vibrating properties play important roles under these conditions.Coherent weakly damped CC bond vibration strength is associated with molecular ordered structure.All-trans-β-carotene has highly ordered structure and strong coherent weakly damped CC bond vibrating properties,which lead to large RSCS in the solvent with large density and low concentration at low temperature.     

含苯乙烯桥侧链三枝分子的二阶非线性光学性质

采用密度泛函理论B3LYP/6-311+g(d,p)方法对含苯乙烯桥侧链均三嗪类衍生物的8个分子(Y1-Y8)进行几何构型优化,对其最优构型采用TD-DFT(TDB3LYP/6-311+g(d,p)),计算电子吸收光谱,用有限场FF方法及自编程序计算二阶非线性光学（NLO）性质。结果表明,8个分子的μ（或0）值为104数量级个原子单位(10-29 esu),显示出良好的二阶非线性光学性能。在其三支链的末端引入强供电子基团（如-N(CH3)2或-N(CH2CH3)2）比引入弱供电子基团及吸电子基团,更有利于改善体系的二阶非线性光学性质,从而可获得良好的非线性光学材料。     

碳碳双键法研究萝卜不同部位的β-胡萝卜素含量分布

β-胡萝卜素广泛存在于植物体中,是典型的线性多稀分子,具有重要的生物功能。由于β-胡萝卜素是碳碳单、双键(C-C,C=C)交替的短链共轭多稀分子,含有大量离域的π电子,具有重要的光电特性。根据Andreas等对拉曼散射强度的研究,当激发光波长落在分子的电子吸收带时,会产生共振拉曼效应,能使拉曼光谱强度提高106倍。利用共振拉曼光谱技术,测量了β胡萝卜素分子及胡萝卜、青萝卜、白萝卜肉质直根不同部位其拉曼光谱,发现含β-胡萝卜素较高的胡萝卜的拉曼光谱与β-胡萝卜素的吻合很好。Gellerman等研究表明,样品浓度与拉曼峰强成正比关系,从拉曼光谱中容易发现三种萝卜的光谱强度纵向根头到主根及横向表皮到根芯逐渐降低,且青萝卜和白萝卜拉曼光谱强度都很低,并在碳碳单键的振动峰处发生峰劈裂。分别计算了碳碳单键和碳碳双键与碳氢键拉曼强度比,三种萝卜的I_CC/I_C-H随着测量部位(横向和纵向)的不同变化幅度接近：胡萝卜的表皮和根芯纵向的变化率分别为A₁=0.213 3和A₂=0.215 9,青萝卜表皮外和里的变化率分别为B₁=0.219 1和B₂=0.211 4,白萝卜表皮外和里分别为D₁=0.223 9和D₂=0.224 1;而对于I_C-C/I_C-H随着测量部位不同其变化率相差很大：胡萝卜的变化率a₁=0.212 1和a₂=0.232 4,青萝卜的变化率b₁=0.263 5和b₂=0.268 7,白萝卜的变化率d₁=0.369 0和d₂=0.304 9。对比发现三种萝卜的碳碳单键与碳氢键振动强度比随着测量部位的不同变化幅度相差很大,而从碳碳双键与碳氢键振动强度比发现三种萝卜中不同部位的β胡萝卜含量有相似的分布。这是由于青萝卜和白萝卜中β-胡萝卜素的含量少, 随着测量部位的不同C-C伸缩振动峰发生峰劈裂, 即在1 130和1 156 cm-1处出现两个振动峰, 经过计算和分析这两个峰都属于碳碳单键的伸缩振动峰, 且随着β-胡萝卜素含量的减少C-C整体的强度降低, 劈裂的新峰峰强度却有增加的趋势, 这使得原峰位的峰强度大幅度降低, 这与计算I_C-C/I_C-H的结果一致,不同品种的萝卜中β-胡萝卜素含量随测量部位的不同变化幅度截然不同。因此, 当样品中β-胡萝卜含量较少时,利用C=C振动峰峰强度同时分析样品不同部位的β-胡萝卜素含量分布变化会更准确。同时,研究和了解萝卜中不同部位β-胡萝卜素的含量为日常消费和膳食营养提供了很好的理论依据。     

液芯光纤共振拉曼光谱法检测水中生物分子研究

拉曼光谱是研究水中生物分子重要的有效方法之一,然而由于拉曼散射截面小,特别是水分子的电子激发态能级高,因此水中生物分子的拉曼光谱测量甚为困难。将液芯光纤技术和共振拉曼技术结合起来,可大幅度提高拉曼光谱强度。实验中用可以获得最大的共振拉曼光谱强度的514.5 nm Ar+离子激光激发,分别用石英和Teflon液芯光纤对水中β-胡萝卜素生物分子进行了痕量检测研究。结果表明应用石英液芯光纤和Teflon液芯光纤可分别检测浓度为10-7～10-9mol·L-1和10-9～10-10mol·L-1的β-胡萝卜素。     

Recent advances in linear and nonlinear Raman spectroscopy. Part VII

The aim of this paper is to provide an overview of advances in the field of Raman spectroscopy as reflected in articles published each year in the Journal of Raman Spectroscopy as well as in trends across related journals publishing in this research area. The context for this review is derived from statistical data on article counts obtained from Thomson Reuters ISI Web of Knowledge by year and by subfield of Raman spectroscopy. Additional information is gleaned from presentations featuring Raman spectroscopy presented at the International Conference on Advanced Vibrational Spectroscopy in Kobe Japan in August 2013 and at SCIX 2013 sponsored by the Federation of Analytical Chemistry and Spectroscopy Societies in Milwaukee, Wisconsin, USA, October 2013. Papers published in the Journal of Raman Spectroscopy in 2012 are highlighted in this review and reflect topics and advances at the frontier of Raman spectroscopy, a field that is expanding rapidly as a sensitive photonic probe of matter at the molecular level in an ever widening sphere of novel applications. Copyright © 2013 John Wiley & Sons, Ltd.     

Investigation of nonlinear absorption and aggregation in aqueous solutions of rhodamine B using thermal lens technique

Thermal lensing effect was studied in aqueous solutions of rhodamine B using 532 nm, 9 ns pulses from a Nd:YAG laser. A low intensity He-Ne laser beam was used for probing the thermal lens. Results obtained show that it is appropriate to use this technique for studying nonlinear absorption processes like two photon absorption or excited state absorption and for analyzing dimerization equilibria.     

具有不同取代基团的香豆素系列分子二阶非线性光学性质的DFT研究

本文设计了具有不同取代基团的7-苯乙烯基香豆素和4-苯乙烯基香豆素的A、B两个系列共14个化合物分子。采用密度泛函理论B3LYP/6-31G方法对其几何构型进行了全结构优化．在所得优化结构的基础上对这些分子的稳态二阶非线性光学（NLO）系数β值进行计算分析,同时用含时密度泛函理论（TD-DFT）对这些分子的电子性质进行了研究．结果表明：此类香豆素化合物具有较大的分子β值,其中A类分子的共面性好,共轭链长,β值均比B类分子的大．14个化合物中前线分子轨道能级差越小的化合物,其βtot值越大．各分子前线分子轨道跃迁对二阶NLO效应有明显的贡献．     

基于二阶离散变分方法的非线性映射参数估计

提出一种估计非线性映射未知参数的二阶离散变分方法.首先针对非线性离散混沌系统, 利用变分方法导出了伴随方程和目标泛函梯度, 以此为基础利用二阶离散变分方法给出了二阶伴随方程和精确计算Hessian矩阵-向量乘积的显式表达式; 其次设计了估计非线性映射未知参数的新算法, 并以此对Hyperhenón映射和二维抛物映射中的未知参数进行了精确的估计. 数值仿真结果表明了该方法的有效性和优点. 关键词： 非线性映射 参数估计 二阶离散变分方法 伴随方程     

Molecular dynamics in low vibrational states investigated by fs time-resolved coherent anti-Stokes Raman spectroscopy technique

The molecular dynamics process is investigated in this paper using a broadband fs time-resolved coherent anti-Stokes Raman spectroscopy (CARS) technique. By varying the timing of laser pulses, low vibrational states are started and studied on both the electronically excited B(³Π_0u⁺) state and ground X(¹Σ_0g⁺) state of iodine in the gas phase at room temperature. According to change the pump wavelength or Stokes pulse as well as the wavelength of the detection window for the CARS signal, dynamics on different potential-energy surfaces can be accessed and detected by the CARS spectroscopy. Results show that the period of the oscillation is decreased for the excited B(³Π_0u⁺) state as the wavelength of the pump pulses is increased, while it is increased for the ground X(¹Σ_0g⁺) state with the increase of the Stokes wavelength.     

SERS investigation of interfacial water at a silver electrode in acetonitrile solutions

Surface-enhanced Raman scattering from a silver electrode in solution of 0.1 M LiClO₄ in acetonitrile has been analyzed as a function of applied potential. Three ν(O-H) bands associated with the interfacial water and two ν(O-H) bands associated with the OH⁻ ion species were observed depending on the electrode potential. The band at 3487 cm⁻¹ is favored at relatively positive potentials and assigned to H₂O molecules interacting with the electrode surface via the oxygen atoms. Another band at 3586 cm⁻¹ appears in a wider potential region and is assigned to the H₂O molecules with one or both of the hydrogen atoms facing the electrode surface. Additionally, evidence for the possible surface ion pair, Li⁺OH⁻, which is closely associated with H₂O molecules and the quasi-crystalline form of LiOH are also presented in this paper.     

Applications of Raman spectroscopy in herbal medicine

Raman spectroscopic techniques are a group of chemical fingerprint detection methods based on molecular vibrational spectroscopy. They are compatible with aqueous solutions and are time saving, nondestructive, and highly informative. With complementary and alternative medicine (CAM) becoming increasingly popular, more people are consuming natural herbal medicines. Thus, chemical fingerprints of herbal medicines are investigated to determine the content of these products. In this study, I review the different types of Raman spectroscopic techniques used in fingerprinting herbal medicines, including dispersive Raman spectroscopy, resonance Raman spectroscopy, Fourier transform (FT)–Raman spectroscopy, surface-enhanced Raman scattering (SERS) spectroscopy, and confocal/microscopic Raman spectroscopy. Lab-grade Raman spectroscopy instruments help detect the chemical components of herbal medicines effectively and accurately without the need for complicated separation and extraction procedures. In addition, portable Raman spectroscopy instruments could be used to monitor the health and safety compliance of herbal products in the consumer market.