共查询到20条相似文献,搜索用时 140 毫秒
1.
引言化学露光计是用来测定光强的光化学反应体系,一种好的露光计在一定的波长下,其量子产率是完全确定的。本文应用已知的草酸铁钾露光计标定光强,藉以测定偶氮苯光异构化反应的量子产率。早在1957年Zimmerman等人首次提出偶氮苯可以作为露光计,继而,在1976年Gauglitz 用动力学方法直接测得其量子产率。我们的工作是在吸收了Gauglitz方法优点的基础上,对偶氮苯光异构化反应量子产率的测定方法加以改进,将计算机的作用从简单计算扩大到对动力学经验方程的拟合,从而简化了实验操作,并能获得比较 相似文献
2.
本文报道一类新的由9,10-二氰基蒽(CcA)敏化的α-蒎烯异构化为苧烯和顺式罗勒烯的光化学反应。在苯溶液中形成苧烯的量子产率为0.32,是乙腈溶液中的8倍,提出了经由单重激发态激态复合物形成苧烯和经由三重激发态激态复合物形成顺式罗勒烯的反应历程,并从实验数据的动力学分析中得到了证实。 相似文献
3.
本文首次报导了双氮桥式配体双铑(d~-—d~7)络合物Rh_2L_4在可见光辐照下与氯代烃发生光化学反应。四种络合物的量子产率皆具有波长依赖性并与溶剂和轴向配体的性质有关。光化学反应产物经快速原子质谱和闪光光解法鉴定。另外, 将光化学反应产物和电解产物进行了ESR和循环伏安法的对比测定。结果表明, 标题络合物与氯代烃发生不可逆的一电子光诱导转移反应, 生成Rh_2L_4Cl。 相似文献
4.
5.
6.
将红外光谱的基本原理和实验技术应用于光化学反应过程及产物结构的测定研究中。通过实验结合实验原理,可直观地观察到安息香在光化分解反应中前后光谱的变化,以及在不同溶剂所得不同产物的实验结果。有助于理解光化学反应机理,掌握红外光谱实验技术。 相似文献
7.
光化学反应机理模式的概述光化学是研究电子重新分布的所谓电子激发态分子反应的。光化学反应是与同时发生的物理现象,即光物理,例如,光的辐射和吸收、热量的变化等密切相关。现代光化学反应机理的研究发展了化学反应性及结构理论的基本概念。这使实验化学家们可以用描述基态反应中电子移动方 相似文献
8.
9.
溶液荧光量子产率的相对测量 总被引:4,自引:1,他引:3
本文基于光疏溶液中量子产率相对测量的理论公式,建议一种荧光量子产率的简易测量法——等吸点激发,校正荧光发射谱积分面积比法。本法简便易行,适应性宽,能获得较好的精密度和准确度。实验表明,本法成功的关键在于消除溶剂或试剂空白的散射和荧光背景的影响,提出了消除这些影响的具体方法。 相似文献
10.
采用激光闪光光解-瞬态吸收光谱技术研究了355nm激光作用下芘四磺酸钠(PyTS)水溶液的光化学反应机理及其产生水合电子的动力学行为.研究首次发现PyTS水溶液激发单线态(PyTS1*)在260nm、激发三线态(PyTS3*)在300nm及阴离子自由基(PyTS-?)在330nm处的特征吸收峰;分析了生成的水合电子(e-aq)的主要反应途径包括自猝灭反应及与PyTS的反应,得到水合电子与PyTS反应的准一级速率常数为2.7′105s-1;并计算得到在此实验条件下,PyTS水溶液经双光子吸收产生的水合电子量子产率为3.2′10-2. 相似文献
11.
An experiment is described where a bright luminescence of a razor‐blade from an electric razor can be generated even by a 4, 5 Volt battery. The luminescence is not produced by the metal itself but by solution particles in its immediate vicinity. This conversion of electrical energy into light is explained and the influence of different parameters on the quantum yield is discussed. By this simple and appealing experiment instructors are encouraged to introduce topics of modern research and technology into the curriculum. 相似文献
12.
A practical synthetic route to regorafenib, in which the target compound was obtained via a 10-step synthesis starting from 2-picolinic acid, 4-chloro-3-(trifluoromethyl)aniline, and 3-fluorophenol, is reported. Crucial to the strategy is the preparation of 4-amino-3-fluorophenol via Fries and Beckman rearrangements using an economical and practical protocol. The main advantages of the route include inexpensive starting materials and an acceptable overall yield. A scale-up experiment was carried out to provide regorafenib with 99.96% purity in 46.5% total yield. 相似文献
13.
Alteration of polymorphic selectivity through different crystallization mechanisms occurring in the same crystallization solution 总被引:1,自引:0,他引:1
We report a case in which two different crystallization mechanisms occurring in the same crystallization experiment are found to yield different polymorphic outcomes. In particular, we focus on crystallization of glycine from neutral aqueous solution. Crystallization in the bulk solution gives only the metastable alpha-polymorph, as observed in previous studies, whereas crystallization by evaporation of a thin film of the solution on the walls of the crystallization vessel is found to give rise to the thermodynamically stable gamma-polymorph, and furthermore produces an uncharacteristic crystal morphology for this polymorph. A detailed set of control experiments are described that elucidate mechanistic details relating to the latter crystallization process. The fact that crystallization on the walls of a crystallization vessel can yield a different polymorphic outcome from crystallization in the bulk solution in the same experiment has potentially much wider significance with regard to other polymorphic systems. 相似文献
14.
《Chemical physics letters》2002,350(5-6):555-560
A method to grow multi-wall carbon nanotube bundles in a high yield (weighing over 15 times the catalyst) is developed and a plausible explanation for the formation and high yield of the bundles is suggested. The Co–Mo–Mg–O catalyst used in the experiment is prepared by a sol–gel technique, molybdenum being doped into the catalyst through oxidation and diffusion at 750 °C. Small changes to the catalyst preparation lead to the growth of single-wall carbon nanotubes (SWNTs). Our work is an exploitation of the high performance of the solid catalyst in the synthesis of novel nanomaterials. 相似文献
15.
A. Kodre M. Hribar D. Glavič 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1986,2(3):173-176
An attempt is made to measure the relative intensities of the resonant Raman scattering and the corresponding Auger process. A multiwire proportional counter is employed to distinguish the two processes. The experiment on krypton at theK-edge supports the conjectured constant fluorescence yield for photon energies below the edge, allowing a shift of less than ±10% of the above-edge value. The experiment leads to an improved method of determining fluorescence yields. TheK-shell fluorescence yield of krypton is remeasured to 0.660±0.007. 相似文献
16.
17.
We describe a two-dimensional solid-state NMR technique to investigate membrane protein topology under magic-angle spinning conditions. The experiment detects the rate of (1)H spin diffusion from the mobile lipids to the rigid protein. While spin diffusion within the rigid protein is fast, magnetization transfer in the mobile lipids is an inefficient and slow process. Qualitative analysis of (1)H spin-diffusion build-up curves from the lipid chain-end methyl groups to the protein allows the identification of membrane-embedded domains in the protein. Numerical simulations of spin-diffusion build-up curves yield the approximate insertion depth of protein segments in the membrane. The experiment is demonstrated on the selectively (13)C labeled colicin Ia channel domain, known to have a membrane-embedded domain, and on DNA/cationic lipid complexes where the DNA rods are bound to the membrane surface. The experiment is designed for X-nucleus detection, which could be (13)C or (15)N in the protein and (31)P for the DNA. Finally, we show that a qualitative distinction between membrane proteins with and without a membrane-embedded domain can be made even by using an unlabeled protein, by detection of lipid signals. This spin-diffusion experiment is simple to perform and requires no oriented bilayer preparations and only standard NMR hardware. 相似文献
18.
19.
Martin Abell 《Trends in analytical chemistry : TRAC》1984,3(3):VII-X
The trend in analytical chemistry toward statistically designed experiments is reinforced by the trend toward using personal computers. The tedious calculations required to determine which factors significantly affect the performance or yield of an experiment are easily done with one of the 'electronic spreadsheet' programs now available on personal computers. 相似文献
20.
Knochenmuss R 《Journal of mass spectrometry : JMS》2002,37(8):867-877
A quantitative model of primary ionization in ultraviolet matrix-assisted laser desorption/ionization (UV-MALDI) is presented. It includes not only photochemical processes such as exciton pooling, but also the effects of the desorption event. The interplay of these two is found to be a crucial aspect of the MALDI process. The desorbing plume is modeled as an adiabatic expansion with entrained clusters. The parameters in the model are defined as much as possible via experiment or by analogy with known effects. The model was applied to the matrix 2,5-dihydroxybenzoic acid and found to reproduce the fluence dependence of the fluorescence yield and key features of the picosecond two-pulse ion generation efficiency curves. In addition, the model correctly predicts a fluence rather than irradiance threshold, the magnitude of the threshold, the magnitude of the ion yield, laser wavelength effects, plume temperatures, plume expansion velocities and the spot size effect. 相似文献