Neutral molecular cluster formation of sulfuric acid-dimethylamine observed in real time under atmospheric conditions
Neutral molecular cluster formation of sulfuric acid-dimethylamine observed in real time under atmospheric conditions
复制标题
DOI：
10.1073/pnas.1404853111
复制
发表时间：
2014-10-21
影响因子：
11.1
通讯作者：
Curtius, Joachim
中科院分区：
文献类型：
--
作者：
Kuerten, Andreas;Jokinen, Tuija;Curtius, Joachim
对于大气中的硫酸（SA）浓度的二甲胺（DMA）的存在下，在万亿分之几的体积混合比可以解释观察到的边界层新的颗粒形成率。然而，由于缺乏合适的仪器，中性（不带电）集群的浓度和分子组成还没有报道。在这里，我们报告的实验，从宇宙离开室外液滴室在欧洲核研究组织揭示形成的中性粒子含有多达14 SA和16 DMA分子，对应于约2 nm的流动性直径，在大气相关条件下。这些测量弥合了成核的分子和粒子观点之间的差距，揭示了粒子形成和生长的基本过程。中性簇被发现形成或接近动力学极限，其中颗粒的形成仅限于SA分子的碰撞率。尽管中性颗粒对于SA二聚体向前的蒸发是稳定的，但由于凝聚和壁损失，含有约10个SA分子的1.7纳米尺寸颗粒的形成速率比二聚体的形成速率小4个数量级。颗粒直径达到1.7纳米之前的损失。这表明，无论是大气粒子的形成率，也不依赖于SA可以简单地解释在集群蒸发或临界核的分子组成。
For atmospheric sulfuric acid (SA) concentrations the presence of dimethylamine (DMA) at mixing ratios of several parts per trillion by volume can explain observed boundary layer new particle formation rates. However, the concentration and molecular composition of the neutral (uncharged) clusters have not been reported so far due to the lack of suitable instrumentation. Here we report on experiments from the Cosmics Leaving Outdoor Droplets chamber at the European Organization for Nuclear Research revealing the formation of neutral particles containing up to 14 SA and 16 DMA molecules, corresponding to a mobility diameter of about 2 nm, under atmospherically relevant conditions. These measurements bridge the gap between the molecular and particle perspectives of nucleation, revealing the fundamental processes involved in particle formation and growth. The neutral clusters are found to form at or close to the kinetic limit where particle formation is limited only by the collision rate of SA molecules. Even though the neutral particles are stable against evaporation from the SA dimer onward, the formation rates of particles at 1.7-nm size, which contain about 10 SA molecules, are up to 4 orders of magnitude smaller compared with those of the dimer due to coagulation and wall loss of particles before they reach 1.7 nm in diameter. This demonstrates that neither the atmospheric particle formation rate nor its dependence on SA can simply be interpreted in terms of cluster evaporation or the molecular composition of a critical nucleus.