Stabilization of sulfuric acid dimers by ammonia, methylamine, dimethylamine, and trimethylamine
Stabilization of sulfuric acid dimers by ammonia, methylamine, dimethylamine, and trimethylamine
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DOI：
10.1002/2014jd021592
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发表时间：
2014-06-27
影响因子：
4.4
通讯作者：
Hanson, David R.
中科院分区：
文献类型：
--
作者：
Jen, Coty N.;McMurry, Peter H.;Hanson, David R.
本研究通过实验探索氨 (NH3)、甲胺 (MA)、二甲胺 (DMA) 和三甲胺 (TMA) 如何影响包含两个硫酸分子（二聚体）的电中性簇的化学形成机制。二聚体还可能含有无法检测到的化合物，例如水或碱，这些化合物在电离和采样时会蒸发。使用玻璃流动反应器进行测量，该反应器含有稳定的湿润氮气流，硫酸浓度为10(7) 至10(9) cm(-3)。将已知摩尔流量的碱性气体注入流动反应器中。明尼苏达大学簇化学电离质谱仪用于测量产生的硫酸蒸气和簇浓度。结果发现，对于给定浓度的硫酸蒸气，二聚体浓度随着碱性气体浓度的增加而增加，最终达到稳定水平。二聚体浓度饱和时的碱浓度表明 NH3 < MA < TMA。 DMA 形成稳定的硫酸二聚体。开发了两种通过酸碱反应形成簇的启发式模型来解释数据。该模型提供了与观测结果一致的蒸发速率常数范围，并得出了与大气观测结果一致的成核速率的分析表达式。
This study experimentally explores how ammonia (NH3), methylamine (MA), dimethylamine (DMA), and trimethylamine (TMA) affect the chemical formation mechanisms of electrically neutral clusters that contain two sulfuric acid molecules (dimers). Dimers may also contain undetectable compounds, such as water or bases, that evaporate upon ionization and sampling. Measurements were conducted using a glass flow reactor which contained a steady flow of humidified nitrogen with sulfuric acid concentrations of 10(7) to 10(9) cm(-3). A known molar flow rate of a basic gas was injected into the flow reactor. The University of Minnesota Cluster Chemical Ionization Mass Spectrometer was used to measure the resulting sulfuric acid vapor and cluster concentrations. It was found that, for a given concentration of sulfuric acid vapor, the dimer concentration increases with increasing concentration of the basic gas, eventually reaching a plateau. The base concentrations at which the dimer concentrations saturate suggest NH3 < MA < TMA. DMA in forming stabilized sulfuric acid dimers. Two heuristic models for cluster formation by acid-base reactions are developed to interpret the data. The models provide ranges of evaporation rate constants that are consistent with observations and leads to an analytic expression for nucleation rates that is consistent with atmospheric observations.