Complex Acid-Base Chemistry in Minimal Solvation Environments - The Case of Atmospheric New Particle Formation

在这个由化学系化学结构、动力学和机理-A项目和大气与地球空间科学系大气化学项目共同资助的项目中，斯托尼布鲁克大学的克里斯托弗约翰逊教授正在开发一种定量描述直接从大气气体形成气溶胶颗粒所涉及的基本分子相互作用的方法。这一过程占大气中气溶胶颗粒的很大一部分。 对气溶胶粒子形成的基本机制还没有很好的了解，导致其对气候变化影响的不确定性。由于新形成的颗粒的亚纳米尺寸，很难使用常规测量来研究它们。创造这些粒子的新技术与最近开发的激光光谱学方法相结合，以研究驱动这些粒子形成的化学过程。这些结果有助于改进新粒子形成的模型，这些模型可用于改进天气和气候模型。在执行这项工作的过程中，从高中到研究生院的年轻研究人员都参与了复杂仪器和分析工具的设计，建造和修改。该项目的重点是在最少或没有溶剂的情况下发展对酸碱化学的新理解。虽然溶剂中的酸碱化学已被充分理解，但新颗粒的形成主要是通过空气中的酸碱化学发生的，并且水蒸气在颗粒形成中的作用尚未得到很好的确定。在质谱仪中生成一些酸和碱分子的簇，这些分子选自那些预期在新粒子形成中发挥作用的分子，并一次研究一种特定的成分。在离子阱中，团簇暴露于大气痕量蒸气中，它们的生长由质谱法确定。每个集群组合物的特征在于结构上使用振动光谱和大力使用温度控制的离子阱。这些结果揭示了驱动生长的能量因素，分子如何在颗粒中排列，质子在酸和碱之间转移的作用，以及大气蒸汽是否整合到酸碱盐结构中或结合到其表面。 这些结果有助于改进新粒子形成的模型，这些模型可用于改进天气和气候模型。

In this project, which is jointly funded by the Chemical Structure, Dynamics, and Mechanisms-A program of the Chemistry Division and the Atmospheric Chemistry Program of the Division of Atmospheric and Geospace Science, Professor Christopher Johnson of Stony Brook University is developing a quantitative description of the fundamental molecular interactions involved in the formation of aerosol particles directly from atmospheric gases. This process accounts for a significant fraction of aerosol particles in the atmosphere. The underlying mechanisms governing aerosol particle formation are not well understood, leading to uncertainty about their impact on climate change. Due to the sub-nanometer size of newly formed particles, it is difficult to study them using conventional measurements. New techniques to create these particles are combined with recently developed laser spectroscopy methods to investigate the chemistry driving the formation of these particles. The results aid the refinement of models of new particle formation that can be used to improve weather and climate models. In the course of performing this work, young researchers from high school through graduate school are involved in the design, construction, and modification of sophisticated instrumentation and analysis tools.This project focuses on the development of a new understanding of acid-base chemistry with minimal or no solvent. Though acid-base chemistry in solvents is well understood, new particle formation occurs largely via acid-base chemistry in air, and the role of water vapor in particle formation has not been well established. Clusters of a few acid and base molecules, chosen from those expected to play a role in new particle formation, are generated in a mass spectrometer and studied one specific composition at a time. In ion traps, clusters are exposed to atmospheric trace vapors and their growth is determined by mass spectrometry. Each cluster composition is characterized structurally using vibrational spectroscopy and energetically using temperature-controlled ion traps. These results reveal the energetic factors driving growth, how molecules arrange in the particle, the role of proton transfer between the acids and bases, and whether atmospheric vapors integrate into the acid-base salt structure or bind to its surface. The results aid the refinement of models of new particle formation that can be used to improve weather and climate models.