Synthesis and Photophysics of Core‐Substituted Naphthalene Diimides: Fluorophores for Single Molecule Applications

The synthesis and photophysics of two new aminopropenyl naphthalene diimide (SANDI) dyes are reported. A general and convenient method for the synthesis of the precursor mono‐, di‐, and tetrabrominated 1,4,5,8‐naphthalene tetracarboxylic dianhydrides is described. The two core‐substituted SANDIs exhibit many of the photophysical properties required for fluorescence labeling applications including high photostability and high fluorescence quantum yields (>0.5) in the visible region of the spectrum. The emission wavelength is sensitive to the number of substituents on the NDI core, and the fluorescence decay times are in the range of ～8–12 ns for both compounds in the solvents investigated. Preliminary fluorescence emission data from single molecules of the compounds embedded in poly(methyl methacrylate) films are also reported and show that single molecules have very low yields of photobleaching, particularly the di‐substituted system. Furthermore, only a small proportion (<10 %) of the single molecules studied display fluorescence intermittencies or “blinks” in their photon trajectory. The compounds appear to be excellent candidates for applications at the single molecule level, for example, as FRET labels.     

线型三原子分子在强激光场中多光子激发的李代数方法

使用二次非谐振子模型和Magnus近似方法构造了在强激光场下线型三原子分子的振动哈密顿并推导出时间演化算符的代数形式,在此基础上研究了线型DCN分子的跃迁几率随外场的频率和强度的变化关系,表明了多光子跃迁谱的特点.     

单分子光子源信号背景比的研究

通过在不同信号背景比下的最佳信号噪声比分析,讨论单分子光子源背景信号分别为时间均匀分布和指数特性分布时同步取样时间的选取.在Hanbury-Brown-Twiss探测方式下,测量光子源的单事件光子统计概率P(n,n=0、1、2).研究给出在P(1)2P(2)-3P(2)时,直接测量单分子光子源的信号背景比的方法SBR=[P(1)]2/2P(2).当信号背景比SBR>2.41时研究给出判别单分子的方法P(2)<(2-4-2n-)2/2,n为每个激发周期内探测到的平均光子数.     

一种新型双共轭链分子非线性光学性质的理论研究

对实验室合成的双共轭链分子1,4-二(4-二乙胺基苯乙烯基)-2-［4-(N-甲基-N-羟乙基)氨基-4′-硝基偶氮苯］-5-己烷氧基苯(BSBAB)及合成它的单共轭链分子的单光子和双光子吸收特性在从头计算的基础上利用密度泛函理论进行了研究.分子BSBAB的优化结构显示，组成该分子的横链和纵链除了保持各自的共轭面外，几近相互垂直.因此，分子BSBAB较好地继承了两个单共轭链分子的光学特性.计算结果表明，在低能量范围内，分子BSBAB具有三个双光子吸收峰，分别来自于两个单共轭链分子以及两者的耦合作用.从理论上证明了双共轭链分子BSBAB是一种具有宽带强双光子吸收的分子材料.理论结果和实验结果符合得较好.在HF水平上的响应函数方法进一步证实了有限态求和方法计算结果的可靠性.还给出了电荷转移态的电荷迁移过程. 关键词： 双光子吸收 双共轭链有机分子 非线性光学     

Resonant tunnelling of the magnetization in molecular crystal of [（Mn1-xCrx）12O12 （CH3COO）16（H2O）4]·2CH3COOH·4H2O（x=0,0.03,0.04,0.05）

The quantum tunnelling of magnetization （QTM） in single crystals of the single molecule magnet （Mn1-xCrx）12- Ac （x=0, 0.03, 0.04, 0.05） has been investigated. In comparison with its parent Mnl2-Ac, a greater rate of magnetization relaxation and a lower effective potential-energy barrier have been observed in Cr-doping samples. This modulation of QTM due to the Cr-doping could be attributed to the small change of Sz due to the smaller spin of Cr itself and additional intrinsic but distributed transverse and longitudinal anisotropy raised by a subtle change of the local environment in the magnetic Mn12 core.     

Accurate studies on dissociation energies of diatomic molecules

The molecular dissociation energies of some electronic states of hydride and N2 molecules were studied using a parameter-free analytical formula suggested in this study and the algebraic method (AM) proposed recently. The results show that the accurate AM dissociation energies DeAM agree excellently with experimental dissociation energies Deexpt, and that the dissociation energy of an electronic state such as the 23△g state of 7Li2 whose experimental value is not available can be predicted using the new formula.     

Analysis of influence of atmosphere extinction to Raman lidar monitoring CO2 concentration profile

Lidar （Light detection and ranging） system monitoring of the atmosphere is a novel and powerful technique tool. The Raman lidar is well established today as a leading research tool in the study of numerous important areas in the atmospheric sciences. In this paper, the principle of Raman lidar technique measurement CO2 concentration profile is presented and the errors caused by molecular and aerosol extinction for CO2 concentration profile measurement with Raman lidar are also presented. The standard atmosphere extinction profile and ＇real-time＇ Hefei area extinction profile are used to conduct correction and the corresponding results are yielded. Simulation results with standard atmosphere mode correction indicate that the errors caused by molecule and aerosol extinction should be counted for the reason that they could reach about 8 ppm and 5 ppm respectively. The relative error caused by Hefei area extinction correction could reach about 6%. The errors caused by the two components extinction influence could produce significant changes for CO2 concentration profile and need to be counted in data processing which could improve the measurement accuracies.     

抽运光强度对光学抽运重水气体产生THz激光的影响分析

利用半经典理论，对脉冲光学抽运重水气体产生THz激光信号过程进行分析，对其中抽运光强度与输出THz信号光之间的关系进行了数值计算和求解，结果表明，THz信号出射光强度跟抽运源入射光强度之间不满足简单的线性关系，而是呈现高阶的非线性关系.在工作介质腔长、气压和工作温度一定的条件下，存在最佳抽运光强度，在一定的抽运光强范围内，THz信号出射光强度与抽运源入射光强度的关系呈现近似线性的增长关系，抽运光能量和信号光能量之间的转换效率相对较高，当抽运光强超过一定值时，由于瓶颈效应的发生会导致THz输出信号的逐步减弱，并产生一定的频率调谐范围.     

Synthesis of novel cyclodextrin derivatives by aromatic spacer insertion and their inclusion ability

Novel cyclic host molecules were synthesized by the insertion of three types of aromatic spacers into the skeleton of permethylated α-cyclodextrin. These host molecules formed a 1:1 complex with sodium 3- and 4-nitrobenzenesulfonates (3- and 4-NBS), and sodium 2,4-dinitrobenzenesulfonate (DNBS) in D₂O/CD₃OD (4:1) solution. The type of spacer inserted remarkably affected the inclusion ability of the hosts toward DNBS. The p-xylylene-inserted CDs showed greater inclusion ability toward DNBS than permethylated α- and β-CDs.     

Molecular Schrödinger–Riccati Calculations: The Potential Energy Curve of the Hydrogen Molecule

The Schrödinger–Riccati equation has been used in the study of the potential energy curve of the Hydrogen molecule. The minimum is obtained at the equilibrium bond distance. The predicted total energy at that point is ?1.1727 hartree, with a relative error (in absolute value) of 0.15% with respect to the exact energy of ?1.1745 hartree.