CIMS Sulfuric Acid Detection Efficiency Enhanced by Amines Due to Higher Dipole Moments: A Computational Study

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• 作者：Oona Kupiainen-M??tt? ; Tinja Olenius ; Theo Kurtén ; Hanna Vehkam?ki
• 刊名：Journal of Physical Chemistry A
• 出版年：2013
• 出版时间：December 27, 2013
• 年：2013
• 卷：117
• 期：51
• 页码：14109-14119
• 全文大小：385K
• ISSN：1520-5215

文摘

Quantum chemical calculations have been performed on negatively charged nitric acid鈥搒ulfuric acid鈥揹imethylamine clusters. The cluster energies were combined with a kinetic model to study the chemical ionization of sulfuric acid molecules and sulfuric acid鈥揹imethylamine clusters with nitrate ions. Both the sulfuric acid monomer and the H₂SO₄路(CH₃)₂NH cluster get ionized, but the cluster has a much higher dipole moment, and thus a higher collision rate with charger ions. Clustering of sulfuric acid with bases will therefore increase its detection probability in the CIMS, instead of decreasing it as has been suggested previously. However, our comparison of different quantum chemical methods shows some uncertainty on the extent of sulfuric acid鈥揹imethylamine cluster formation in typical ambient conditions, and no experimental data is available for comparison. Apart from affecting CIMS measurements, the degree of clustering is directly linked to the formation rate of larger clusters, and needs to be quantified in order to understand atmospheric new-particle formation. On the basis of the different charging efficiencies of the monomer and the cluster, a method is proposed for determining experimentally the binding energies of H₂SO₄路base clusters by measuring the extent of cluster formation as a function of base concentration.