Heterogeneous Atmospheric Chemistry: Elucidating the Importantce of Reactions Involving Aqueous Droplets and Ice Crystals Through Cluster Research

该项目旨在确定机制并量化对大气具有重要意义的非均质过程的速率。这些过程的全部过程包括通过形成新的粒子或通过吸附或溶解到微滴或气溶胶粒子上，以及伴随的化学转化，将分子从气态转移到凝聚态。这些过程可以用来从气相中去除物种，从而改变它们的寿命、传输和去除过程，同时影响它们进一步参与气相反应，并增强凝聚相中可能发生的反应。本提案的主旨是通过对星团的研究，旨在阐明反应的机制，这些反应涉及由与(一些)气溶胶、云滴和冰晶有关的液体介质组成的水体系。将在上述每个领域进行一些关键实验，包括旨在阐明水相中的转变以及各种中性和离子物种的影响的工作。拟议的研究被细分为四个一般领域。第一个重点是深入研究涉及水团簇的反应，既有纯的，也有包含其他成分的，以及重要的大气分子和自由基。还将对水与其他分子(如盐和酸)之间的混合簇合物系统进行调查，并确定各种共簇物种在结构和成键上的作用。第二个领域与上述有关，涉及混合团簇的热化学研究。这方面工作的主要目标是提供数据，根据这些数据确定与液滴相互作用的组分的分压(与活度系数有关)。这项工作的第三个方面涉及研究光对第一个领域中被确定为重要的反应的影响。第四项活动是该计划的计算阶段，该计划致力于阐明在该计划的其他三个阶段中确定的对反应和活度系数至关重要的簇状物种的结构和成键。对团簇的振动频率和相关动力学方面的计算将对解释前三个领域的拟议研究结果有价值。

This project is directed to identifying the mechanisms and quantifying the rates of atmospherically important heterogeneous processes. The full range of these processes includes the transfer of molecules from the gaseous to the condensed state by new particle formation or by adsorption onto or dissolution into a microdroplet or aerosol particle, together with concomitant chemical conversion. These processes can serve to remove species from the gas phase, thereby altering their lifetimes, transport and removal processes, and at the same time influencing their further participation in gas phase reactions and enhancing those possible in the condensed phase. The thrust of the present proposal is on studies designed to elucidate the mechanisms of reactions which involve aqueous systems comprising the liquid media associated with (some) aerosols, cloud droplets and ice crystals through an investigation of clusters. Some critical experiments will be conducted in each of the aforementioned areas, including work designed to elucidate transformations in aqueous phases and the influence of various neutral and ionic species. The proposed studies are subdivided into four general areas. The first, to which major emphasis will be given, constitutes an in-depth investigation of reactions involving water clusters, both pure and containing other constituents, along with important atmospheric molecules and free radicals. An investigation of mixed cluster systems between water and other molecules such as salts and acids, along with a determination of the role of various co-clustered species on the structure and bonding, will also be undertaken. The second area, which is related to the aforementioned, involves an investigation of the thermochemistry of mixed clusters. The primary objective of this aspect of the work is to provide data from which to determine the partial pressure of constituents interacting with droplets (related to activity coefficients). The third aspect of the work involves studies of the influence of light on the reactions identified to be important in the first area. The fourth activity constitutes a calculational phase of the program devoted to elucidating the structure and bonding of cluster species identified in the other three phases of the program as being of critical importance to the reactions and the activity coefficients. Calculations of vibrational frequencies and related dynamical aspects of clusters will be of value in interpreting the results of the proposed studies in the first three areas.