Dynamics of Ion-Radical Collisions: Imaging Studies

在这个由化学系化学结构、动力学和机制计划以及化学测量和成像计划支持的项目中，罗切斯特大学的James Farrar教授及其研究小组将探索自由基与原子或分子离子的碰撞。 通过采用自由基（如CH 3和C3 H5）的脉冲超声源，以及低能阳离子（如N2+、N+、C+、Si+和S+）和阴离子（如O-、O2-和OH-）的电子撞击或放电源，速度空间成像方法将用于检测反应产物，产生动能和角度的微分截面。特别感兴趣的是产生C-C、C-O、C-N、N-O、S-C和Si-C键的键形成反应。对于阴离子反应，还将检测到由缔合分离产生的自由电子。 这些实验将代表对低能离子与自由基反应的首次动力学研究，并将解决不包括离子-自由基反应的放电和行星大气化学模型的严重缺陷。除了表征上述化学系统的动力学，这项研究将提供对反应性模式的更深入理解和对放电中发生的化学反应（例如反应性离子蚀刻中涉及的那些）的分子理解，以及大气和外星化学。仪器技术的发展可能对化学的各个分支学科产生影响，包括质谱和离子成像。参与这项研究的研究生、本科生和博士后将通过开发新的测量技术、新的高附加值产品和进一步培训科学人员，为国家科学和经济基础设施做出贡献。

In this project supported by the Chemical Structure, Dynamics and Mechanisms Program and the Chemical Measurement and Imaging Program of the Division of Chemistry, Professor James Farrar of the University of Rochester and his research group will explore the collisions of free radicals and atomic or molecular ions. By employing a pulsed supersonic source of free radicals such as CH3 and C3H5, and an electron impact or discharge source of low energy cations such as N2+, N+, C+, Si+, and S+, and anions such as O-, O2-, and OH-, velocity space imaging methods will be used to detect the products of the reactions, yielding differential cross sections in kinetic energy and angle. Of particular interest are the bond formation reactions that yield C-C, C-O, C-N, N-O, S-C, and Si-C bonds. For anionic reactions, free electrons produced by associative detachment will also be detected. The experiments will represent the first dynamical studies of the reactions of low energy ions with free radicals and will address the serious deficiencies of models for electrical discharges and the chemistry of planetary atmospheres that do not include ion-radical reactions.In addition to characterizing the dynamics of the aforementioned chemical systems, this research will provide a deeper understanding of reactivity patterns and a molecular understanding of the chemistry that takes place in electrical discharges such as those involved in reactive ion etching, and in atmospheric and extraterrestrial chemistry. The instrumental technique development may have impacts in various subdisciplines of chemistry, including mass spectrometry and ion imaging. The graduate and undergraduate students and post-doctoral associates involved in this research will contribute to the national scientific and economic infrastructure through the development of new measurement technologies, new high value-added products, and the further training of scientific personnel.