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

在这个由化学结构、动力学和机制--化学系的一个项目和大气和地球空间科学系的大气化学项目共同资助的项目中，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形成气溶胶颗粒所涉及的基本分子相互作用进行定量描述。这一过程占了大气中气溶胶颗粒的很大一部分。控制气溶胶颗粒形成的潜在机制尚未得到很好的理解，导致对其对气候变化的影响存在不确定性。由于新形成的颗粒是亚纳米级的，很难用传统的测量方法来研究它们。创造这些颗粒的新技术与最近发展的激光光谱学方法相结合，以研究这些颗粒形成的化学驱动因素。这些结果有助于改进新粒子形成的模型，这些模型可以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参与了复杂仪器和分析工具的设计、建造和修改。本项目专注于发展对酸碱化学的新理解，使用最少或没有溶剂。尽管人们对溶剂中的酸碱化学已有很好的了解，但新粒子的形成主要是通过空气中的酸碱化学进行的，而水蒸气在粒子形成中的作用还没有很好地确定。从那些有望在新粒子形成中发挥作用的分子中挑选出几个酸和碱分子的簇，在质谱仪中产生，并一次研究一种特定的组成。在离子陷阱中，星团暴露在大气中的痕量蒸气中，它们的生长由质谱仪确定。使用振动光谱和能量使用温度控制的离子陷阱来表征每个簇合物的结构。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，这些模型可以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.