Chemistry for Sustainable Development
Chemistry for Sustainable Development
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化学促进可持续发展
DOI：
10.1007/978-90-481-8650-1_3
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
Dyke J
中科院分区：
文献类型：
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作者：
Dyke J
利用光离研究气相反应中间体提供了获得中性和离子键能以及阳离子振动常数信息的重要途径，并且更广泛地提供了对其电子结构和反应性的深入了解。本报告概述了从南安普顿PES小组最近的研究调查中可以获得的信息，特别是(i)以ClO和BrO自由基为例，利用气相反应制备活性中间体进行研究。综述了利用原子分子反应制备用于PES研究的反应性中间体的方法，确定反应性中间体存在所必需的实验步骤，以及电子结构和弗兰克-康登因子计算在为特定反应性中间体分配PE光谱带中的重要性。（ii）测量反应速率系数，以大气中重要的反应Cl2+ DMS为例。摘要介绍了如何将流管与光电子能谱仪相连接以获得双分子反应的速率系数。考虑Cl2+ DMS反应可以证明这一点。该反应通过反应中间体Me2SCl2进行，最终产物是CH3SCH2Cl + HCl。在室温下测定了反应速率系数，并讨论了该值对大气化学的影响。同时，还确定了反应中间体的结构。它可以被认为是一个三角双锥体结构，氯原子在轴向位置，甲基和S孤对在平伏位置。（三）用同步辐射研究对大气有重要意义的反应性中间产物，以原子氮为例。总结了用同步辐射研究活性中间体与用固定频率惰性气体放电的光子源相比的优点。考虑到最近对氮原子（一种在高层大气中很重要的反应中间体）的研究，说明了从角分辨恒离子态（CIS）和阈值光电子能谱中获得的额外信息。
Studying a reactive intermediate in the gas-phase with photoionization provides an important way of obtaining information on neutral and ionic bond energies and cationic vibrational constants, as well as more generally of providing insight into its electronic structure and reactivity.This presentation provides an overview of the information that can be obtained by taking recent examples of research investigations from the Southampton PES group, notably(i)Preparation of reactive intermediates for study using gas-phase reactions, taking the ClO and BrO radicals as examples. A review is given of the use of atom-molecule reactions to prepare reactive intermediates for study by PES, the experimental steps which are necessary to establish the presence of a reactive intermediate, and the importance of electronic structure and Franck-Condon factor calculations in assigning the PE spectral bands to a particular reactive intermediate.(ii)Measurement of reaction rate coefficients, using the atmospherically important reaction Cl2+ DMS as an example. A summary is given of how a flow-tube can be interfaced to a photoelectron spectrometer to obtain rate coefficients of bimolecular reactions. This is exemplified by considering the reaction Cl2+ DMS. This reaction proceeds via a reactive intermediate, Me2SCl2, and the final products are CH3SCH2Cl + HCl. The reaction rate coefficient has been determined at room temperature and the implications of the value obtained to atmospheric chemistry are considered. Also, the structure of the reactive intermediate has been established. It can be thought of as a trigonal bipyramidal structure with the Cl atoms in axial positions, and the methyl groups and the S lone pair in equatorial positions.(iii)Study of reactive intermediates of atmospheric importance with synchrotron radiation, using atomic nitrogen as an example. The advantages of using synchrotron radiation to study reactive intermediates compared to using a fixed frequency photon source from an inert gas discharge are summarised. The extra information to be obtained from angularly resolved constant-ionic-state (CIS) and threshold photoelectron spectroscopy are illustrated by considering recent studies on atomic nitrogen, a reactive intermediate which is important in the upper atmosphere.