环戊酮光电离解离的实验和理论研究

本文介绍了真空紫外光电离质谱结合理论计算研究环戊酮单分子的光电离解离过程. 在9.0∽15.5 eV能量范围内,测量了环戊酮离子及其碎片离子的光电离效率曲线. 通过光电离效率曲线,将环戊酮分子的电离能确定为9.23±0.03 eV,并确认碎片离子为：C₅H₇O⁺,C₄H₅O⁺,C₄H₈⁺,C₃H₃O⁺,C₄H₆⁺,C₂H₄O⁺,C₃H₆⁺,C₃H₅⁺,C₃H₄⁺,C₃H₃⁺,C₂H₅⁺, C₂H₄⁺. 利用量子化学计算方法,在ωB97X-D/6-31+G(d,p)理论水平基础上,提出了C₅H₈O⁺的解离机制. 通过对环戊酮解离路径的分析,发现开环和氢迁移过程为环戊酮离子解离的主要路径.     

分子团簇表面吸附敏化ZnO纳米线的第一性原理研究

ZnO纳米线作为新型太阳能电池结构的重要组成部件之一, 其导电能力直接影响到太阳能电池的性能. 采用密度泛函理论平面波超软赝势方法, 计算并分析了C₂H₆O(乙醇)、 C₆H₅FS(4-氟苯硫酚)、 C₇HF₇S(4-(三氟甲基L)-2, 3, 5, 6-四氟硫代苯酚) 等小分子吸附的六边形结构\langle0001angle ZNWs (ZnO 纳米线) 的几何结构、 吸附能和电子结构. 首先, 通过几何优化得到了不同基团吸附的ZNWs的稳定结构, 同时吸附能计算结果表明C₇HF₇S吸附的体系结构最为稳定, 且吸附呈现放热反应; 其次, 为研究表面敏化对导电性能的影响, 计算了不同小分子基团吸附下的能带结构和态密度, 并利用能带理论分析了表面吸附敏化对禁带宽度的调控机理, 结果分析表明小分子表面吸附敏化对ZNWs的电学性能有一定的影响, 其中C₇H₇FS和C₆H₅FS分子均发生了不同程度的电荷转移.     

氯化苯并咪唑镧的荧光光谱

对新合成的化合物氯化苯并咪唑镧HCl₄·[C₇H₆N₂(H₂O)₂]₂La及其LaCl₃·5H₂O的水溶液进行了三维荧光光谱测定,讨论了HCl₄·[C₇H₆N₂(H₂O)₂]₂La在不同波长的光激发下的荧光特性,荧光强度与浓度的关系及标题化合物的上转换荧光,即在540nm绿光的激发下可以获得紫外光(290nm)和近紫外光(360nm).     

甲基环己烷在9∽15.5 eV能量区的真空紫外光电离研究

利用具有同步辐射源的反射式飞行时间质谱仪,研究甲基环己烷的真空紫外光电离和光解离. 观测到母体离子C₇H₁₄⁺和碎片离子C₇H₁₃⁺,C₆H₁₁⁺,C₆H₁₀⁺,C₅H₁₀⁺,C₅H₉⁺,C₄H₈⁺,C₄H₇⁺和C₃H₅⁺的光电离效率曲线. 测定甲基环己烷的电离能为9.80±0.03 eV,通过光电离效率曲线确定其碎片离子的出现势. 在B3LYP/6-31G(d)水平上对过渡态、中间体和产物离子的优化结构进行表征,并使用G3B3方法计算其能量. 提出主要碎片离子的形成通道. 分子内氢迁移和碳开环是甲基环己烷裂解途径中最重要的过程.     

Raman光谱方法研究三氯甲烷与苯分子间的 C/H···π相互作用

测量了不同浓度三氯甲烷(CHCl₃)与苯(C₆H₆) 二元溶液的Raman光谱,随C₆H₆浓度的增加, 受分子间C/H···π相互作用的影响, CHCl₃中C-H键伸缩振动频率向低波数移动;当 CHCl₃体积分数小于40%, C-H键伸缩振动频率不变, 分子间C/H···π相互作用达到饱和.分别以 CHCl₃和 C₆H₆体积分数为70%的 CHCl₃-C₆H₆混合溶液为研究对象, 测量了它们的高压和低温Raman光谱.根据 CHCl₃中C-H键伸缩振动频率随压强和温度的变化关系, 得出了分子间C/H···π相互作用对压强和温度的扰动表现出不稳定性.     

VOxH2O (x= 1——-5)团簇的结构及稳定性研究

用密度泛函理论(DFT),在B3LYP/DZP水平上对H₂O分子与VO_x形成的团簇VO_xH₂O (x= 1---5)进行结构优化、能量和频率的计算,研究了团簇的稳定结构、稳定性和频率特性.结果表明VO_xH₂O (x= 1---5) 团簇的基态构型的电子态均为²A, 对称性均属C₁对称点群,其中x= 1, 4, 5时基态构型中水分子已被解离.水分子倾向于吸附在团簇VO_x上, 形成VO_xH₂O (x= 1---5)团簇. VO_xH₂O (x= 1---5)团簇中, VO_xH₂O (x= 1,4,5) 的化学活性小于VO_xH₂O (x= 2, 3)的化学活性.此外, H₂O体系与VO_x之间的结合强弱顺序为 VO₄H₂O > VO₅H₂O > VOH₂O > VO₃H₂O > VO₂H₂O. VOH₂O中离解出H原子的能量为2.88 eV和从VO₅H₂O中离解出OH基团的能量为2.38 eV, 均在可见光能量范围内,这两个化学过程有可能在可见光催化条件下进行.可以通过团簇的红外和拉曼谱特征, 初步判断水分子在VO_xH₂O团簇中是否离解.     

异补骨脂素热解实验和理论研究

利用同步辐射真空紫外光电离质谱技术,在不同光子能量下,研究了异补骨脂素(C₁₁H₆O₃)的低压热解,探测了不同温度下异补骨脂素的热解产物及其与前驱体的比例. 实验结果表明,异补骨脂素的主要热解产物是CO及其依次消去CO的产物(C₁₀H₆O₂和C₉H₆O). 利用密度泛函理论计算异补骨脂素的解离途径,并利用过渡态理论计算了竞争通道的反应速率常数. 通过实验和理论的结合,确定了异补骨脂素主要解离路径和相应产物的分子结构.     

交叉分子束研究氟原子与1,2-丁二烯反应动力学

利用通用型交叉分子束研究了氟原子与1,2-丁二烯的反应,观测到了C₄H₅F+H反应通道. 测量产物C₄H₅FF在实验坐标下的角度分辨的飞行时间谱,获得了这个通道质心坐标下的产物角分布和动能分布. 实验结果表明,相对于氟原子束方向,产物C₄H₅FF主要是后向散射,同时也有大量的前向散射. 这表明反应通道主要通过长寿命的络合物形成机理进行的,同时也伴有直接的双分子亲核取代反应(SN2)机理.     

有机分子超薄膜的结构对摩擦的影响

采用分子动力学方法, 模拟了由脂肪酸C_nH_2n+1COOH}和C₁₇H₃₁COOH (n=12,13,14,15,16,17)组成的混合单层Langmuir-Blodgett(LB)膜间的摩擦特性, 探究了膜结构的变化对超薄膜的摩擦的影响. 结果显示. 在滑动过程中, 随着n的增加, 膜内分子的运动受到邻近分子的约束逐渐增加, 膜结构的稳定性也逐渐增加, 其剪切压逐渐减小, n=17时的剪切压最小. 在两单层膜之间无氢键形成; 而混合膜内的分子之间形成的氢键是单层膜结构稳定的主要因素, 其中n=16时形成的氢键最稳定, 但全部由相同C₁₇H₃₁COOH分子组成的单层膜的滑动效果最好. 分子的弯曲形变能对剪切压影响非常小.     

环戊烯分子内价轨道1a′的电子动量谱学研究

报道了环戊烯（C₅H₈）分子1a′轨道的电子动量谱，并且给出了价 轨道的电离能谱信息 .实验在非共面对称几何条件下用能量多道型电子动量谱仪完成，入射电子的能量为1200 eV 加结合能.通过Hartree-Fock 和密度泛函方法计算得到了C₅H₈分子 1a′轨道的动量谱. 对1a′轨道的电子动量谱的实验值和理论计算进行了比较，得到了该轨道的极强度（pole s trength）的信息.     

液体中静态介电常数随温度渡越行为及其关联特征研究

为了通过液体静态介电常数随温度的变化行为,归纳总结液体中分子间取向关联极化的一般规律,在现有的文献中,筛选了分子的电子极化远小于分子间取向关联极化的18种液体材料,并对其静态介电常数随温度的变化行为进行了分析研究.结果表明,液体中静态介电常数随温度变化存在一个普遍的渡越行为,并且对应于该种渡越,至少存在两种分子之间的取向关联序,一种随温度降低而增强,而另一种则减弱.     

Dielectric absorption in mixtures of anisole with some primary alcohols at microwave frequency

Dielectric properties of binary mixtures of anisole with methanol (MeOH), 1-propanol (1-PrOH), 1-butanol (1-BuOH) and 1-heptanol (1-HeOH) over an entire concentration range have been studied at a fixed temperature 40°C. The dielectric constant (ε′) and dielectric loss (ε″) of the binary mixtures of polar liquids have been determined at a microwave frequency of 9.1?GHz. The static dielectric permittivity (ε ₀) of the liquid samples was also determined using a precision LCR meter. Determined values of static dielectric permittivity (ε ₀) and dielectric permittivity (ε*) at 9.1?GHz frequency were used to evaluate relaxation time (τ) and high frequency limit dielectric permittivity (ε _∞). Dielectric parameters were interpreted in terms of molecular interaction between the anisole and alcohol molecules.     

On the theory of dielectric relaxation

The Kirkwood expression for the static dielectric constant of a polar substance is extended to non-zero frequencies by a means which avoids the introduction of spherical specimens and the connection between the dipoledipole correlation functions of distinct spatial regions. The procedure is based on a previously derived relation between the dynamic dielectric constant and the current-current susceptibility and on the use of the Callen-Welton theorem to relate the susceptibility to fluctuations. Surface effects are eliminated at the outset by consideration of media which are infinite in extent. A general relation between the long-range dipole-dipole correlations (which fall off as the inverse cube of the distance) and short-range correlations in a specimen composed of non-polarizable molecules is found from a consistency relation. It is shown that the two microscopic relaxation times which result from the existence of but one relaxation time in the dielectric constant correspond to the transverse and longitudinal relaxation times with the longitudinal time being screened relative to the transverse time by the static dielectric constant.     

A renormalization group analysis of correlation functions for the dipole gas

We develop a renormalization group method for analyzing the generating functional for charge correlations of a dilute classical dipole gas. It is based on and extends the renormalization group analysis introduced by Brydges and Yau for the dipole gas partition function. Our method leads to systematic formulas for the large-distance behavior of correlation functions of all orders. We prove that in any dimensiond2, at any value>0 of the inverse temperature, and at sufficiently small activityz, the correlation functions exhibit at large distances the same behavior as for a vacuum (z=0), but with a new dielectric constant 1+ over which we have good control. The results proved here extend existing results on the two-point correlations to all higher correlations, and constitute a general confirmation of the fact that dipoles do not screen.     

等静压下0.75Pb（Mg1/3Nb2/3）O3-0.25PbTiO3陶瓷的介电性能研究

研究了等静压对0.75Pb（Mg_1/3Nb_2/3）O₃-0.25PbTiO₃（PMN-25PT）陶瓷介电温谱的影响,PMN-25PT剩余极化随等静压变化和等静压压致相变.结果表明,随着压力增加,PMN-25PT的介电峰值温度T_m降低,/+{dT_m}/-{dP}≈-4℃/kbar,极化弛豫增强;剩余极化随压力增加连续减小;介电常数对压力的依赖关系与对温度场的依赖相似,压力诱导PMN-25PT发生弛豫铁电—顺电相变,相变为宽化的渐变过程,频率色散和极化弛豫更加强烈和普遍. 关键词： 铌镁酸铅-钛酸铅 等静压 介电弛豫 压致相变     

Study of heterogeneous interaction in binary mixtures of 2-methoxyethanol-water using dielectric relaxation spectroscopy

The dielectric relaxation measurements on binary mixtures of 2-methoxyethanol with water have been carried out over entire concentrations and at temperature range of 0 °C to 25 °C using a picosecond time domain reflectometry technique. The complex dielectric permittivity spectra of 2-methoxyethanol/water mixtures were fitted using Havriliak-Negami equation. The static dielectric constant and relaxation time for all concentrations were obtained using least square fit method. The principal relaxation time is small if compared to that of corresponding alcohol/water mixtures this may be due to the hydrogen bonding ether oxygen in the 2-ME-water system. Excess dielectric properties, Kirkwood correlation factor, thermodynamic properties and Bruggeman factor are also determined and the results are interpreted in terms of heterogeneous interactions among the unlike molecules due to hydrogen bonding.     

基于分数傅里叶变换的分数相关峰值特性

本文通过理论分析和计算机仿真研究了分数傅里叶变换的级次对分数相关峰值特性的影响并优化了分数相关的级次。结果表明分数相关输出在旁辩和峰值宽度方面与传统相关相比有了较大的改善,因而可以提高目标探测的灵敏性。     

A theory of electric polarisation in liquids : I. Nonpolar liquids

The static dielectric constant of nonpolar liquids is described by analyzing the pair distribution function and the dipole-dipole interaction into a finite set of Fourier components. In a mean field approximation the theory leads to a final formula that does not contain any adjustable parameter, and proves to work better than the Clausius-Mossotti equation. The theory explains in a satisfactory way the temperature and pressure dependence of the dielectric constant of nonpolar liquids, as well as the temperature variation of the refractive index of many organic polar liquids.     

Partial structures and compressibilities of ions in fused potassium bromide

Treating the coulomb interaction between ion species as a perturbation on the Waisman-Lebowitz solution for direct correlation function within the hard core region, the total direct correlation function in K-space has been formulated, which gives a direct method of evaluating the partial structure factors between different ion species of the fused salts through the use of Pearson-Rushbrooke equations. The partial structure factors so obtained have been applied to evaluate the partial radial distribution functions of ion pairs. In addition, many other important associated functions such as the static correlations of total number, mass and charge densities have been computed by particular linear combination of partial structure factors. The charge neutrality relate the partial structure factors to the isothermal compressibility for the wavevectorK → 0 and hence the evaluation of the compressibilities of ions in fused KBr is possible, which agrees well with the observed value. As such the present method is very useful in investigating the structure of molten salts since only the parametersσ _ij , the distances of closest approach between ions andɛ, the effective dielectric constant (which can be estimated from the literature) are enough for this work.     

Pressure and temperature dependences of the dielectric constant,Raman spectra and lattice constant of SnI42

The pressure and temperature dependences of the Raman frequencies, static dielectric constant and lattice constant of the molecular crystal SnI₄, were investigated. These results are combined to evaluate the pure volume and pure temperature (i.e. volume-independent) dependences of the molecular polarizability and of the Raman-active phonon self-energies. The pressure results also allow the separation of the Raman modes into external and internal modes of the crystal; the external modes exhibit a much stronger pressure dependence, and thereby larger Grüneisen parameters, than do the internal modes. The Raman frequencies increase (decrease) with increasing pressure (temperature) whereas the dielectric constant increases with both increasing pressure and temperature, emphasizing the importance of non-volume effects. In fact, it is found that the isobaric temperature dependence of the dielectric constant is dominated by the pure temperature dependence of the molecular polarizability. The pure volume dependence of the polarizability, on the other hand, is relatively small as is perhaps typical of most molecular crystals.