Ortega Ismael K, Donahue Neil M, Kurtén Theo, Kulmala Markku, Focsa Cristian, Vehkamäki Hanna
Laboratoire de Physique des Lasers, Atomes et Molécules , Université Lille 1, 59655 Villeneuve d'Ascq, France.
Center for Atmospheric Particle Studies, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States.
J Phys Chem A. 2016 Mar 10;120(9):1452-8. doi: 10.1021/acs.jpca.5b07427. Epub 2015 Nov 18.
Highly oxidized organic molecules may play a critical role in new-particle formation within Earth's atmosphere along with sulfuric acid, which has long been considered as a key compound in this process. Here we explore the interactions of these two partners, using quantum chemistry to find the formation free energies of heterodimers and trimers as well as the fastest evaporation rates of (2,2) tetramers. We find that the heterodimers are more strongly bound than pure sulfuric acid dimers. Their stability correlates well with the oxygen to carbon ratio of the organics, their volatility, and the number of hydrogen bonds formed. Most of the stable trimers contain one sulfuric acid and two organics (1,2), whereas many (2,2) tetramers evaporate quickly, probably due to the stability of (1,2) clusters. This finding agrees with recent experimental studies that show how new-particle formation involving oxidized organics and sulfuric acid may be rate-limited by activation of (1,2) trimers, confirming the importance of this process in the atmosphere.
高度氧化的有机分子可能与硫酸一起，在地球大气中的新粒子形成过程中发挥关键作用，长期以来硫酸一直被视为这一过程中的关键化合物。在这里，我们利用量子化学方法来探究这两种成分之间的相互作用，以找出异二聚体和三聚体的生成自由能以及(2,2)四聚体的最快蒸发速率。我们发现，异二聚体的结合力比纯硫酸二聚体更强。它们的稳定性与有机物的氧碳比、挥发性以及形成的氢键数量密切相关。大多数稳定的三聚体包含一个硫酸和两个有机物(1,2)，而许多(2,2)四聚体蒸发迅速，这可能是由于(1,2)团簇的稳定性所致。这一发现与最近的实验研究结果一致，这些研究表明，涉及氧化有机物和硫酸的新粒子形成可能受(1,2)三聚体活化的速率限制，从而证实了这一过程在大气中的重要性。
