Optical absorption spectra of linear and cyclic thiophenes—selection rules manifestation

We theoretically study the size-dependent relation between absorption spectra of thiophene-based oligomers and the corresponding cyclothiophenes. In our approach based on a Frenkel exciton Hamiltonian, we demonstrate that the geometry and selection rules determine the observed relations between the spectra.     

Calculation of Normal Vibrations of Chlorin by the Method of Density Functionals

Using the DFT/B3LYP method with a 6-31G(d) basis set, the structure, normal vibration frequencies, and the absolute band intensities in the IR spectra of the chlorin molecule and its four symmetric isotopomers have been calculated. Scaling of the force field by the Pulay method in independent and natural coordinates has been carried out. A method for obtaining effective force fields without using experimental data on the fundamental vibration frequencies is proposed. By comparing the vibration modes and constructing special matrices, complete assignment of the fundamental frequencies of porphin and chlorin has been carried out. It has been shown that the majority of porphin macroring vibrations upon pyrrolenine ring hydrogenation are frequency-characteristic and only 12 vibrations change considerably. A frequency correlation with regard for the mode transition between chlorin and all its isotopomers under consideration has been established. Comparative analysis of the force fields of porphin and chlorin in dependent natural coordinates has revealed the unique nonlocal character of the change in force constants of the macroring upon hydrogenation of one pyrrolenine ring. Modeling of the IR spectra of chlorin and its isotopomers has been performed. Assignment and interpretation of the normal vibrations of the molecules under consideration have been carried out.     

Density-Functional Theory Calculations of Normal Modes and Raman Intensities for Tetraazaporphin

The structure, harmonic frequencies, and nonresonance Raman intensities for porphin, tetraazaporphin (TAP), and three of its isotopomers are calculated by the density-functional theory of B3LYP/6-31G(d). Scaling of force constants for porphin in nonredundant natural coordinates is performed. The scaling factors obtained were used to predict the force field and normal modes of TAP and three of its isotopomers. Two alternative methods are used to carry out reliable assignment of the TAP frequencies: wavenumber-linear scaling method and frequency-shift method. There is good agreement between the frequencies predicted within the framework of the three methods used. The conservativeness of the out-of-plane B _2g - and B _3g -modes for porphin and TAP is examined. The Raman spectrum for TAP is simulated. A refinement of the assignment of the experimental frequencies for TAP of even symmetry types on the basis of the calculations performed is made.     

放射性9C束流不同贯穿深度上的线能谱测量

为阐述放射性⁹C束流应用于治癌的物理基础, 运用一个球形生物组织等效正比计数器测量了⁹C束流不同贯穿深度上的线能谱, 得到了沿束流贯穿深度上的剂量平均线能分布. 将实验测量得到的线能谱转换成为不同传能线密度在吸收剂量中所占份额的分布, 得到了该⁹C束流在不同贯穿深度上的剂量平均传能线密度分布. 将生物组织等效正比计数器测量得到的与先前通过平行板正比计数器测量得到的该⁹C束流的剂量平均传能线密度分布进行比较, 发现: 在束流入射通道上, 两者测量数据符合很好, 而在束流Bragg峰附近⁹C离子的沉积区域, 由组织等效正比计数器测量得到的剂量平均传能线密度值大于由平行板正比计数器测量得到的值.     

Measurements of Time-Varying Characteristics of Optical Signals and Inhomogeneities of Tested Substances with Additional Phase Modulation

The problem of investigation of the amplitude and phase structure of a time-varying probing optical signal and the structure of time-varying inhomogeneities of a substance tested by this signal is considered. The analysis is concerned, in particular, with determination of the structure of signals and processes with resolution in the pico- and femtosecond range. The scheme used for the analysis is based on registration of four spatially separated spectra of the studied radiation. The spectra are formed in a four-channel scheme with a twin-wave Michelson interferometer and a spectral device. Modulators based on electrooptical crystals (perovskites) are placed in the channels. The sum spectra are formed: without modulators, with the effect of either of the modulators, and with both of them affecting the radiation. The effect of the studied substance implies either modulating the radiation (in this case it is described by multiplication) or redistributing the radiation (then it is described by convolution).     

穆斯堡尔谱法及其应用

文章简介了穆斯堡尔效应、穆斯堡尔谱的产生以及穆斯堡尔效应的应用 ,说明它不仅在理论上具有深刻的意义 ,又有着广泛的应用价值 .     

Changes in the near-edge X-ray absorption fine structure spectra of long-chain diacetylene derivatives through photopolymerization in Langmuir–Blodgett films

Photopolymerization of cadmium 10,12-pentacosadiynoate (CdDA) in Langmuir–Blodgett (LB) films, with the molecular packing well arranged by moderate preannealing, was investigated with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Greenish films of polydiacetylene with an absorption wavelength of 705 nm were obtained through the photopolymerization of preannealed monomer LB films, and this resulted in an extended π-conjugate system based on the well-ordered monomer in a two-dimensional arrangement. The electronic structures of the polydiacetylenes were found to be correlated to the variation of the molecular arrangements in the films from the changes in the NEXAFS spectra through photopolymerization in the LB films. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2329–2336, 2004     

闪光照相条件下相对质量吸收系数的测量

 介绍了闪光照相中X光传播规律的等效单能模型。针对闪光照相出光重复性差、能谱测量困难的特点提出了相对质量吸收系数的概念。阐述了闪光照相中相对质量吸收系数的测量原理和方法。在闪光照相实验设备上采用整条D～L曲线对钨材料相对质量吸收系数进行了测量，得到的实验结果为1.23，与数值模拟结果1.26符合较好。     

滤片-XRD探测系统响应时间测量

 研究了软X射线能谱仪探测道系统(系统包括X射线二极管（XRD）、SUJ-50-10电缆和不同频带示波器)的响应时间。实验利用上海激光联合实验室的20TW激光器激光(激光能量约20J，脉冲宽度约1ps)打金箔靶产生的X光，用XRD探测系统测量，记录示波器有TK684C，TK694C和WM8500等。将实验数据进行了线性拟合和比对分析。滤片XRD探测系统的响应时间随偏压升高而加快，随传输电缆长度的增加而变慢，因此测量快信号过程时，应提高探测器偏压，缩短传输电缆，选择宽频带高采样率示波器，以便减少系统的响应时间，减小信号失真程度。