脉冲激光光声量热装置的研制及用之对香豆素激光染料无辐射跃迁过程的研究

本文报道了一套适用于液相体系的高灵敏度脉冲激光光声量热装置的建立。用此仪器对香豆素激光染料C428, C47和C120的无辐射过程进行了研究, 测得它们在无水乙醇中的无辐射跃迁量子产额分别为0.50, 0.47和0.38。     

取代效应对脂滴检测NAPBr染料分子的双光子吸收和激发态性质影响的理论探究（英文）

双光子荧光染料分子在生物医学成像中具有广阔的应用前景,但取代效应对分子结构以及光物理性质影响的探求相对匮乏.本文设计并研究了一系列脂滴检测染料分子,分析了分子的光学性质以及无辐射跃迁等.通过分子内弱相互作用和电子-空穴布居分析,阐述了其内在机理.结果表明,所研究的分子均具有优良的光物理性能、高效荧光量子产量、大的斯托克斯位移以及显著的双光子吸收截面等.本工作合理地解释了实验现象并阐述了取代效应对脂滴检测NAPBr染料分子的双光子吸收和激发态性质的影响,这为设计新型的高效有机分子提供了理论指导.     

酞菁和卟啉分子的超快内转换和振动弛豫

用微扰密度矩阵和瞬态线性极化率理论,模拟了四特丁基酞菁（BuPc）和四苯基卟啉（TPP）分子的飞秒荧光亏蚀谱．初步定量地确定了它们的Huang-Rhys因子．振动弛豫和电子激发态溶剂化的速率常数．飞秒荧光亏蚀谱在零延时附近的尖峰．归结为S2→S1的内转换所造成的后果．通过对光谱的模拟,比较可靠地确定了内转换速率常数。     

凝聚相中振动能量弛豫的理论研究

凝聚相中的振动能量弛豫是化学、物理学和生物学中一个非常重要的动力学过程.近年来, 许多实验和理论方法业已建立并用来探索它的微观机理.本文简要介绍一些常用理论方法及其应用,并对将来的发展方向作一展望.     

钪和钇二价离子跃迁几率和振子强度的理论计算

利用最弱受约束电子势模型理论计算了二价钪离了和二价钇离子的能级间跃迁几率和振子强度的数值．二价钪离子的计算结果与美国国家标准技术研究院（NIST）所给出的可接受值吻合良好二价钇离子的计算结果也与现有的其他理论方法的计算结果十分接近．     

固体样品的光声位相理论及应用研究

在R-G理论的基础上,考虑了无辐射弛豫过程对位相信号的影响,推导出新的位相公式。研究结果表明,位相(ψ)与吸收系数(β)、热扩散长(μ_s)、弛豫时的延迟时间(τ)和快弛豫与慢弛豫时的热量比(R)有关。并用此公式解释了稀土化合物PrF₃和叶绿素b的位相谱。PrF₃的位相由f-f跃迁的吸收系数决定,而叶绿素b两个吸收带之间的位相差是由快弛豫与慢弛豫时放出的热量比不同产生的。     

含BN旋转轴的光驱动分子马达的理论设计和机理研究

依据B=N键与C=C键的电子结构相似性,以Feringa型二苯乙烯型光驱动分子马达（CC-stilbene）为母体,设计了含极性旋转轴的模型马达BN-stilbene.CASPT2//CASSCF计算结果表明,优化所得的BN-stilbene分子的基态存在四个与CC-stilbene马达结构相似、相对能量一致的螺旋异构体;B=N极性共价双键对BN-stilbene的基态和激发态电子结构有显著影响.对BN-stilbene模型马达的工作机理研究表明,极性旋转轴的引入使得BN-stilbene中S₁/S₀-CI与激发态中间体构型更加相似且能量更低,同时可增加旋转的驱动力,起到改进分子马达光异构化过程的单向性的目的.     

π堆积的腺嘌呤-胸腺嘧啶体系激发态电荷转移和无辐射失活的半经典动力学模拟

采用半经典电子-辐射-离子动力学(SERID)模型模拟了π堆积的腺嘌呤-胸腺嘧啶(A-T)体系激发态的光物理失活过程. 设置激光脉冲仅作用于T, 模拟发现电子由A转移到T, 形成(A⁺T^-)^*激基缔合物(exciplex). 当分子间距缩短至0.300 nm时, 由于轨道离域效应产生电荷重组, 体系恢复电中性; 当A分子的C4'－C5'扭曲程度最大时, 体系通过避免交叉点衰减至基态. Exciplex 的失活途径由分子间距离和A分子的变形程序两个因素决定. 由于A分子的C4'、C5'原子位阻较大, 难以达到失活所必需的强烈扭曲, 因此(A-T)^*的寿命比胸腺嘧啶堆积体系(T-T)^*显著增长.     

C6H6可见光与红外跃迁强度的代数方法计算

Based on the wavefunctions obtained in the calculation of C-H stretching overtones of C6H6 and C6D6 molecules,the visible and infrared transition intensities of the molecules for C-H stretching overtones up to as high as v=0 are described by the Iachello-Oss algebraic model on the symmetric bases. The formula for Raman transition is also given. The operators for the transition are constructed according to the symmetry of the molecule. The construction of the symmetric bases is greatly simplified by using the symmetrized boson representation technique. Combining with the overtones calculation,the present work shows the vibration mode of C-H stretching is the local mode,which is consistent with other works. The agreement between the calculated results and observations is very good. The agreement indicates that the coupling between C-H stretching mode and other modes is weak or the coupling effects can be absorbed in the adjustment of parameters. The high precision calculation of the properties of molecules can be achieved by the algebraic model with fewer parameters compared with the traditional method. It also indicates that the combination of algebraic model and the symmetrized boson representation technique is a very powerful tool for describing the vibration of molecules.     

超快速反应荧光亏蚀谱微观动力学理论

用超短脉冲激发动力学光谱理论在两电子体系下模拟了飞秒时间分辨的荧光亏蚀谱, 再现了实验中所得荧光亏蚀谱的双指数衰减和凹陷两种现象, 这两种现象分别是由于探测脉冲使电子激发态上振动基态和较高振动态的分子受激发射而产生的.     

Theoretical investigation of internal conversion in chromyl chloride

The internal conversion process from single vibronic levels in the first excited electronic state S₁ of chromyl chloride was theoretically investigated. On the basis of this analysis certain important features of the experimentally observed fluorescence decay from S₁ have been understood. Implications of the obtained results to multiphoton chemistry are discussed.     

Some peculiarities of manifestations of the isotope effect in structural transformations of molecules

We consider the effect of the isotopic substitution on the characteristics of structural transformations of molecules. Attention is paid to the probability factor not taken into account in the kinetic isotope effect theory earlier. This factor can prove to be determining in a number of cases, and it results in not only quantitative, but also qualitative changes in the kinetics of the structural transformation process. For example, there may appear or disappear the induction of the reaction and the time dependence of the reaction constant, the inverse ratio of the yields of obtained products, and so on.     

荷电膜的研究进展

荷电膜以其特殊的分离机理,使之与电中性膜相比在分离性能、通量及膜的使用寿命等方面具有不可比拟的优势.大多数的荷电膜是经过一系列物理化学改性制得的,荷电膜材料的研究为新型膜材料的开发拓宽了领域,随着对膜性能要求的日益提高,荷电膜的研究具有重要的意义.本文首先介绍了荷电膜所用到的材料及其用途,并对所用到的材料进行分类,然后重点论述了荷电膜的制备及其表征方法(膜电位的测试方法),最后指出荷电膜需要进一步深入研究的内容.     

膜Zeta电位测试技术研究进展

分离膜荷电化显著地影响着膜的分离性能和耐污染能力。因此,定量化表征膜表面(包括孔表面)电性能具有重要的理论价值和实际意义。本文系统地综述了各种膜Zeta电位测定原理、特点及其不足,并展望了膜Zeta电位的未来研究方向。     

Order-Disorder Structural Phase Transitions in Alkali Perchlorates

Order-disorder structural phase transitions in alkali perchlorates MClO₄ (M=Na, K, Rb, Cs) are investigated using molecular dynamics simulation. The potentials in the simulations are based on the Gordon-Kim modified electron gas formalism extended to molecular ions. The simulations yield first-order phase transitions in perchlorates from low temperature orthorhombic structures to high temperature cubic NaCl structures. The perchlorate ions are found to be orientational disordered in the high temperature phases.     

Recent Developments in Carbon-Based Nanocomposites for Fuel Cell Applications: A Review

Carbon-based nanocomposites have developed as the most promising and emerging materials in nanoscience and technology during the last several years. They are microscopic materials that range in size from 1 to 100 nanometers. They may be distinguished from bulk materials by their size, shape, increased surface-to-volume ratio, and unique physical and chemical characteristics. Carbon nanocomposite matrixes are often created by combining more than two distinct solid phase types. The nanocomposites that were constructed exhibit unique properties, such as significantly enhanced toughness, mechanical strength, and thermal/electrochemical conductivity. As a result of these advantages, nanocomposites have been used in a variety of applications, including catalysts, electrochemical sensors, biosensors, and energy storage devices, among others. This study focuses on the usage of several forms of carbon nanomaterials, such as carbon aerogels, carbon nanofibers, graphene, carbon nanotubes, and fullerenes, in the development of hydrogen fuel cells. These fuel cells have been successfully employed in numerous commercial sectors in recent years, notably in the car industry, due to their cost-effectiveness, eco-friendliness, and long-cyclic durability. Further; we discuss the principles, reaction mechanisms, and cyclic stability of the fuel cells and also new strategies and future challenges related to the development of viable fuel cells.     

Photodissociation of acryloyl chloride in the gas phase

The 193 nm photodissociation dynamics of CH2 CHCOCl in the gas phase has been examined with the technique of time-resolved Fourier transform infrared emission (TR-FTIR) spectroscopy.Vibrationally excited photofragments of CO (≤ 5),HCl (≤ 6),and C2H2 were observed and two photodissociation channels,the C-Cl fission channel and the HCl elimination channel have been identified.The vibrational and rotational state distributions of the photofragments CO and HCl have been acquired by analyzing their fully rotationally resolved v→v-1 rovibrational progressions in the emission spectra,from which it has been firmly established that the mechanism involves production of HCl via the four-center molecular elimination of CH2 CHCOCl after its internal conversion from the S1 state to the S0 state.In addition to the dominant C-Cl bond fission along the excited S1 state,the S1→S0 internal conversion has also been found to play an important role in the gas phase photolysis of CH2 CHCOCl as manifested by the considerable yield of HCl.     

Recent Developments in Lead‐Free Double Perovskites: Structure,Doping, and Applications

Lead‐free perovskite structures have been recently attracting considerable attention because of their eco‐friendly nature and properties, such as their lead‐based structure. In this work, we reviewed the lead‐free double perovskite (LFDP) structure because of its unique electronic dimensions, chemical stability, and substitutional chemistry compared with other lead‐free structures. We highlighted the recent progress on crystal structure prediction, synthesis methods, metal dopants, and ligand passivation on LFDPs. LFDPs are useful for several applications, such as solar cells, light‐emitting diodes, degradation of photocatalytic dyes, sensors, and X‐ray detectors. This report provides a summary of recent progress as a reference for further research on lead‐free perovskite structures.