Development of High-Resolution Laboratory Rapid EXAFS Apparatus Using an Imaging Plate Detector

在动态反应过程中，关键物种的检测对于分子水平上的分析是非常重要的。由于检测和评价反应中间体和短寿命物种的动态行为是动态反应体系分析的关键，我们在这项工作中进行了以下研究：1.使用成像板检测器的停流实验室EXAFS装置的研制停流实验室EXAFS装置由一个以薄板Ge(111)晶体作为色散多色器的测角器、一个快速成像板探测器和一个停流样品混合装置组成。成像板绕着旋转的DRAM滚动，并通过停流组件中的样品室暴露在透射式X射线下。2.利用同步辐射开发时间分辨停流EXAFS系统在…开发中获得的知识基础上在实验室EXAFS装置的基础上，在高能物理国家实验室光子工厂的BL-12C站研制了同步辐射时间分辨停流EXAFS系统。该系统由作为X射线探测器的电离室、快速电流放大器、适合于BL-12C的停流混样装置和用于步进扫描法时间分辨测量的快速A/D转换器组成。由于离子在电离室中的漂移速度，最小时间分辨率约为1ms，所用停流装置的死区时间为3.6ms。3.应用于某些快速反应体系的动态分析。用两台新研制的时间分辨EXAFS装置对下列反应体系的反应中间体进行了结构测定，并对其反应机理进行了探讨：(1)[Fe(CN)_6]与lt；3-与gt；和_L-抗坏血酸之间的氧化还原反应；(2)Fe~(2+)与lt；2+与gt；N，N-二甲基甲酰胺中的[Co(NH_3)_5Cl]和[Co(NH_3)_5Cl]~(2+)&gt；(3)5，10，15，20-四苯基卟啉在乙腈中的形成

The detection of key species in dynamic reaction processes, in which the species change and react in every moment, is quite important for analysis in the molecular level. Because the detection and the evaluation of the dynamic behavior of reaction intermediates and short-lived species are the key points for the analysis in dynamic reaction systems, we have performed the following investigations in this work.1.Development of Stopped-Flow Laboratory EXAFS Apparatus Using an Imaging Plate DetectorThe stopped-flow laboratory EXAFS apparatus consists of a goniometer with a thin plate Ge (111) crystal as a polychromator in the dispersive mode, a fast imaging plate detector, and a stopped-flow sample-mixing apparatus. The imaging plate is rolled around a rotating dram and is exposed to transmitted X-rays through a sample cell in the stopped-flow assembly.2.Development of Time-Resolved Stopped-Flow EXAFS System Using Synchrotron RadiationOn the basis of knowledges obtained in the development o … More f the laboratory EXAFS apparatus, the time resolved stopped-flow EXAFS system using synchrotron radiation has been developed at the BL-12C station of the Photon Factory of the National Laboratory for High Energy Physics. The system consists of ionization chambers as an X-ray detector, fast current amplifiers, the stopped-flow sample-mixing apparatus modified to fit BL-12C,and a fast A/D converter used for the time-resolved mesurement in the step-scanning method. The minimum time-resolution was on the order of 1 ms due to the drift velocity of ions in the ionization chamber, and the dead time was 3.6 ms for the used stopped-flow assembly.3.Application to Dynamic Analysis for Some Fast Reaction SystemsThe structural determination has been performed for the reaction intermediates in the following reaction systems by using two newly developed time-resolved EXAFS apparatus, and then the reaction mechanisms have been evaluated.(1) Redox reaction between [Fe (CN) _6] ^<3-> and _L-ascorbic acid(2) Redox reaction between Fe^<2+> and [Co (NH_3) _5Cl] ^<2+> in N,N-dimethylformamide(3) Metalloporphyrin formation of 5,10,15,20-tetraphenylporphyrin in acetonitrile Less