Effects of the structural order of canthaxanthin on the Raman scattering cross section in various solvents: A study by Raman spectroscopy and ab initio calculation

In this work,we measure the Raman scattering cross sections(RSCSs) of the carbon-carbon(CC) stretching vibrational modes of canthaxanthin in benzene,acetone,n-heptane,cyclohexane,and m-xylene.It is found that the absolute RSCS of CC stretching mode of canthaxanthin reaches a value of 10 24 cm 2 ·molecule 1 ·sr 1 at 8×10 5 M,which is 6 orders of magnitude larger than general RSCS(10 30 cm 2 ·molecule 1 ·sr 1),and the RSCSs of canthaxanthin in various solvents are very different due to the hydrogen bond.A theoretical interpretation of the magnetic experimental results is given,which is introduced in a qualitative nonlinear model of coherent weakly damped electron-lattice vibration in the structural order of polyene chains.In addition,the optimal structure and the bond length alternation(BLA) parameter of canthaxanthin are calculated using quantum chemistry calculation(at the b3lyp/6-31g(d,p) level of theory).The theoretical calculations are in good agreement with the experimental results.Furthermore,the combination of Raman spectroscopy and the quantum chemistry calculation study would be a quite suitable method of studying the structures and the properties of the π-conjugated systems.     

The effect of an anti-hydrogen bond on Fermi resonance： A Raman spectroscopic study of the Fermi doublet v1-v12 of liquid pyridine

The effects of an anti-hydrogen bond on the v1 v12 Fermi resonance （FR） of pyridine are experimentally investigated by using Raman scattering spectroscopy. Three systems, pyridine/water, pyridine/formamide, and pyridine/carbon tetrachloride, provide varying degrees of strength for the diluent-pyridine anti-hydrogen bond complex. Water forms a stronger anti-hydrogen bond with pyridine than with formamide, and in the case of adding non-polar solvent carbon tetrachloride, which is neither a hydrogen bond donor nor an acceptor and incapable of forming a hydrogen bond with pyridine, the intermolecular distance of pyridine will increase and the interaction of pyridine molecules will reduce. The dilution studies are performed on the three systems. Comparing with the values of the Fermi coupling coefficient W of the ring breathing mode v1 and triangle mode v12 of pyridine at different volume concentrations, which are calculated according to the Bertran equations, in three systems, we find that the solution with the strongest anti-hydrogen bond, water, shows the fastest change in the v1-v12 Fermi coupling coefficient W with the volume concentration varying, followed by the formamide and carbon tetrachloride solutions. These results suggest that the stronger anti-hydrogen bond-forming effect will cause a greater reduction in the strength of the v1-v12 FR of pyridine. According to the mechanism of the formation of an anti-hydrogen bond in the complexes and the FR theory, a qualitative explanation for the anti-hydrogen bond effect in reducing the strength of the v1 - v12 FR of pyridine is given.     

光纤中的拉曼效应

在液芯光纤内产生拉曼效应,可以增强自发拉曼、共振拉曼光谱强度10^3倍;降低受激拉曼光谱荫值功率为10^-1．光纤内拉曼效应在科学研究和教学方面都有广泛应用．     

低浓度样品拉曼光谱的实验研究

在液芯光纤内产生共振拉曼效应,可以提高拉曼光谱强度１０＾９倍。测定了１０＾－１０－１０＾－５ｍｏｌ／Ｌ浓度样品的拉曼光谱。实验结果表明,β－胡罗卜素在ＣＳ２中１５２０ｃｍ＾－１拉曼线的强度（散射系数）、频移、线宽随浓度降低而发生变化。     

丙酮CO键在溶剂中频移变化的几种理论模型比较

测量了丙酮在16种溶剂中CO键的伸缩振动拉曼光谱,并且在Gaussian03程序下采用自恰反应场方法(SCRF)对丙酮在各种溶剂中的拉曼光谱进行了理论计算。用三种溶剂模型的电子给体-受体模型、Kirkwood模型和自恰反应场模型对实验结果进行了分析比较,结果表明Gutmann提出的电子给体-受体模型与实验结果符合的最好,而自恰反应场理论结果要好于Kirkwood模型。通过对三种模型的机理进行分析,得出给体-受体模型在解释电负性比较强的分子键振动光谱比较好,自恰反应场模型不但考虑了介电常数ε,而且考虑了分子大小、构型等因素的影响,模型复杂,计算量比较大,但是因为考虑的因素比较多,所以与实验结果也符合的比较好,而Kirkwood模型的主要参数为ε,模型简单,计算简便,能大致反映频移的趋势,说明介电常数是影响频移的一个主要因素。     

溶液浓度对拉曼光谱线宽和频移影响的实验研究

将液芯光纤技术用于傅里叶变换拉曼光谱测量中,提高拉曼光谱强度10²～10⁴倍.应用该技术,在实验上研究了溶液浓度变化对β-carotene,rhodamine在CS²中的CC键π-π^*跃迁拉曼线频移和线宽的影响.实验结果表明,随着浓度降低(1×10^-7～1×10^-12mol/L),拉曼光谱线峰值发生红移,线宽变窄.     

温度对光学纤维自发喇曼光谱强度的影响

测量了不同温度下ＣＣｌ４液芯光纤喇曼光谱强度，实验结果表明，光谱强度随着温度的变化存在着一个极大值，对影响光纤喇曼光谱强度的几个主要因素进行了估算，理论与实验结果符合较好。     

高强聚乙烯纤维的冷等离子体改进

高强聚乙烯纤维的冷等离子体改进金士九，倪亦斌，张佐光（中国科学院化学研究所北京１０００８０）（北京航空航天大学北京）关键词　高强聚乙烯纤维，等离子体，表面改性，界面性能由高强聚乙烯纤维制成的复合材料抗高速撞击（抗弹）性能远远优于芳纶纤维，广泛用作各种...     

溶胶-凝胶法制备纳米二氧化钛颗粒的研究

本文采用钛酸丁脂等原料,利用sol-gel方法制备了TiO2纳米颗粒.研究了不同实验顺序(滴入方式)和工艺参数对制备效果的影响.通过实验和对TiO2纳米粉末的TEM分析,获得了粒度(30-40nm)比较均匀的球型TiO2纳米颗粒.