Temporary Anions and Dissociative Attachment: Probes of Intra- and Intermolecular Interactions

在化学部门实验物理化学项目的这个项目中，Burrow（内布拉斯加州大学）和Jordan（匹兹堡大学）将继续联合实验和理论研究气相取代碳氢化合物中临时阴离子的形成。这两个机构的实验研究将检查振动激发和解离附着（DA）反应，其中产生稳定的阴离子碎片。将测量总DA横截面和临时阴离子形成的垂直附着能（VAEs）。本文将构建一种新的仪器来测量DA产生的片段阴离子的角依赖性。在氯甲烷（CH3Cl）与水等溶剂共膨胀时，将考察溶剂化对暂时阴离子能量和衰变性质的影响。将进行高级电子结构计算，以预测溶剂化如何影响垂直附着能。已占电子态和未占电子态的概念，也称为轨道，提供了一种可视化分子结构和化学反应性的有力手段。光电子能谱长期以来一直是研究已占据轨道的一种手段，但直到最近，通常未占据轨道的相应数据还很少。这项工作旨在收集这些数据，从而帮助回答有关复杂分子结构和键合的关键化学问题。它还为电子转移模型提供了至关重要的数据，电子转移是涉及多种化学过程的机制，如光合作用、光诱导表面解吸、化学致癌和生物修复。

In this project in the Experimental Physical Chemistry Program of the Chemistry Division, Burrow (University of Nebraska) and Jordan (University of Pittsburgh) will continue joint experimental and theoretical studies of temporary anion formation in gas-phase substituted hydrocarbons. Experimental studies at both institutions will examine vibrational excitation and dissociative attachment (DA) reactions in which stable fragment anions are produced. Both total DA cross sections and vertical attachment energies (VAEs) for formation of temporary anions will be measured. A new instrument will be constructed to measure the angular dependence of fragment anions produced by DA. The effect of solvation on the energies and decay properties of temporary anions will be examined in methyl chloride (CH3Cl) co-expanded with solvents such as water. High-level electronic structure calculations will be carried out to predict how the vertical attachment energy is influenced by the solvation. A powerful means of visualizing molecular structure and chemical reactivity is provided by the concept of occupied and unoccupied electronic states, which are also known as orbitals. Photoelectron spectroscopy has long provided a means of studying occupied orbitals, but until recently the corresponding data for normally unoccupied orbitals has been scarce. This work aims at gathering such data, thereby helping to answer key chemical questions on structure and bonding in complex molecules. It also offers data crucial to models of electron transfer, which is the mechanism involved in a large variety of chemical processes, such as photosynthesis, light-induced desorption from surfaces, chemical carcinogenesis, and bioremediation.