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

在这个由化学学部化学结构、动力学和机理a项目和大气与地球空间科学部大气化学项目联合资助的项目中，石溪大学的克里斯托弗·约翰逊教授正在对直接从大气气体中形成气溶胶颗粒的基本分子相互作用进行定量描述。这一过程占大气中气溶胶粒子的很大一部分。控制气溶胶颗粒形成的潜在机制尚不清楚，导致它们对气候变化的影响存在不确定性。由于新形成的颗粒尺寸为亚纳米级，使用常规测量方法很难对其进行研究。制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。在进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。这个项目的重点是发展对酸碱化学的新认识，只有很少或没有溶剂。虽然人们对溶剂中的酸碱化学已经很了解，但新粒子的形成主要是通过空气中的酸碱化学发生的，而水蒸气在粒子形成中的作用尚未得到很好的确定。从那些预计在新粒子形成中起作用的分子中选择一些酸和碱分子的簇，在质谱仪中产生，并一次研究一种特定的成分。在离子阱中，簇暴露于大气痕量蒸汽中，它们的生长由质谱测定。利用振动光谱学和温控离子阱对每个簇的组成进行了结构表征。这些结果揭示了驱动生长的能量因素，分子如何在粒子中排列，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与其表面结合。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.