Theoretical Studies of Heterogeneous Halogen Chemistry on Stratospheric and Tropospheric Ice

9613802 Hynes 在该项目中，将采用量子化学电子结构方法和分子动力学计算机模拟，研究氯和溴物种在大气相关颗粒表面的若干反应速率和机制。这些范围从纯水冰到包括硝酸盐和/或硫酸盐离子的更复杂的表面。在南极平流层和北极对流层中，涉及氯和溴的多相反应与臭氧的催化破坏密切相关。具体实例包括硝酸氯与盐酸的一步反应和涉及硝酸氯水解形成次氯酸的两步形式，次氯酸然后与盐酸反应形成分子氯。也将考虑这些反应的溴类似物以及混合溴/氯的情况。 这项研究将提供全球化学和气候模型所需的反应机制和反应速率。据推测，冰晶格通过质子转移在这些反应中起着重要的催化作用。通常很难通过实验确定一个过程是在一个步骤还是几个步骤中发生的，以及反应是否具有离子特征。

9613802 Hynes In this project, quantum chemical electronic structure methods and molecular dynamics computer simulations will be carried out to study the rates and mechanisms of a number of reactions of chlorine and bromine species on the surface of atmospherically relevant particles. These range from pure water ice to more complex surfaces which include nitrate and/or sulfate ions. Heterogeneous reactions involving chlorine and bromine have been strongly implicated in the catalytic destruction of ozone in the Antarctic stratosphere and in the Arctic troposphee. Specific examples include the one-step reaction of chlorine nitrate with hydrochloric acid and the two- step version involving chlorine nitrate hydrolysis forming hypochlorous acid which then reacts with hydrochloric acid to form molecular chlorine. The bromine analogs of these reactions as well as the mixed bromine/chlorine cases will also be considered. This study will provide reaction mechanisms and reaction rates which are needed as input for global chemistry and climate models. It is hypothesized that the ice lattice plays an essential catalytic role in these reactions via proton transfers. It is often difficult to determine experimentally whether a process occurs in one or several steps, and whether reactions are ionic in character or not.