Spectroscopic, ab initio, and Smog-Chamber Studies of Molecular Aggregates

分子聚集体的光谱、从头算和烟雾室研究

• 批准号: RGPIN-2018-05782
• 负责人: Jäger, Wolfgang
• 金额: $ 13.7万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=747923
• 关键词: Spectroscopic; ab; initio; Smog; Chamber

The research proposal describes a program to study molecular aggregates, which are of relevance to atmospheric chemistry, spanning size regimes from the microscopic, molecular world to the nano-scale. The proposed studies on smaller complexes and clusters are enabled by revolutionary advances in high-resolution rotational spectroscopy in terms of both the development of powerful spectroscopic techniques and developments of effective software to aid in the complex spectroscopic assignment processes. At the heart of theses studies is the characterization of 'critical nuclei', which play a crucial role in the formation and growth of atmospheric aerosol particles. These critical nuclei are thought to consist of several molecules, including organic acids, sulfuric acid, and water, but 'microscopic', spectroscopic analyses have thus far not been provided. Helium nanodroplets can consist of about a thousand to millions of helium atoms, attain a temperature of ~0.4 K, and are superfluid. These properties make them an 'ideal' matrix to study not only unstable molecules, but also low-temperature reactions. Many atmospheric reactions involve radicals and are barrier-less or have low barriers. In addition to radical reactions, for example, between tolyl radical and molecular oxygen, we will also investigate photo-induced reactions. An example is the photo-induced decomposition of oxalic acid, the most abundant dicarboxylic acid in the atmosphere, which could be a major atmospheric sink for this type of compounds. Even larger systems, namely secondary organic aerosol particles and soot particles, will be studied using a photo-reaction or 'smog' chamber. Soot particles are produced in incomplete fossil fuel combustion, for example, and are emitted in great quantities into the atmosphere. Of particular interest is the ageing process of soot particles. Atmospheric soot can be coated with secondary organic aerosol, perhaps produced from organic material also released during fossil fuel burning. This coating changes not only the surface properties of the particle but the increased surface tension causes a collapse of the soot core. Both coating and collapse lead to changes in optical properties and affect the contributions of soot particles to radiative forcing.The proposed research will lead to greater insights into atmospheric processes, including aerosol particle growth and ageing, and the results will have impact on atmospheric modelling and will likely reduce the uncertainties associated with the direct and indirect effects of aerosol on the global climate.

研究建议描述了一个研究分子聚集体的程序，该程序与大气化学相关，该计划涵盖了从微观，分子世界到纳米级的尺寸状态。关于较小的复合物和簇的拟议研究是通过高分辨率旋转光谱的革命进步来实现的，就强大的光谱技术的发展和有效软件的开发而言，可以帮助进行复杂的光谱分配过程。这些研究的核心是“临界核”的表征，它在大气气溶胶颗粒的形成和生长中起着至关重要的作用。这些临界核被认为由几个分子组成，包括有机酸，硫酸和水，但尚未提供“微观”光谱分析。氦纳米圆形可以由大约一千到数百万的氦原子组成，达到约0.4 K，并且是超氟。这些特性使其成为“理想”的矩阵，不仅可以研究不稳定的分子，还可以研究低温反应。许多大气反应涉及自由基，没有障碍或障碍较低。除了自由基反应（例如，在甲甲基自由基和分子氧之间），我们还将研究光诱导的反应。一个例子是草酸的光诱导分解，草酸是大气中最丰富的二羧酸，这可能是这种化合物的主要大气下沉。将使用光电或“烟雾”室研究更大的系统，即二级有机气雾剂颗粒和烟灰颗粒。例如，烟灰颗粒以不完全的化石燃料燃烧产生，并大量发射到大气中。特别有趣的是烟灰颗粒的老化过程。大气烟灰可以用二级有机气溶胶涂覆，也许是由化石燃料燃烧期间释放的有机材料产生的。这种涂层不仅改变了粒子的表面特性，而且表面张力增加会导致烟灰核的塌陷。涂层和塌陷都会导致光学特性的变化，并影响烟灰颗粒对辐射强迫的贡献。拟议的研究将导致对大气过程（包括气溶胶颗粒的生长和衰老）的更多见解，并且结果将影响大气建模，并可能降低与气动剂对全球气候的直接和间接影响相关的不确定性。