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Environ Sci Technol 2014 Dec 18;48(23):13675-84. Epub 2014 Nov 18.

Laboratory of Atmospheric Chemistry, Paul Scherrer Institute , Villigen 5232, Switzerland.

J Phys Chem A 2014 Jul 9;118(29):5464-73. Epub 2014 Jul 9.

Department of Chemistry and Biochemistry, University of Delaware , Newark, Delaware 19716, United States.

The structures and thermochemistry of molecular clusters containing sulfuric acid, water, ammonia, and/or dimethylamine ((CH3)2NH or DMA) are explored using a combination of Monte Carlo configuration sampling, semiempirical calculations, and density functional theory (DFT) calculations. Clusters are of the general form [(BH(+))n(HSO4(-))n(H2O)y], where B = NH3 or DMA, 2 ≤ n ≤ 8, and 0 ≤ y ≤ 10. Cluster formulas are written based on the computed structures, which uniformly show proton transfer from each sulfuric acid molecule to a base molecule while the water molecules remain un-ionized. Read More

J Phys Chem A 2015 Sep 1;119(37):9670-9. Epub 2015 Sep 1.

Division of Atmospheric Sciences, Department of Physics, University of Helsinki , P.O. Box 64, FI-00014 University of Helsinki, Finland.

Despite the well-established role of small molecular clusters in the very first steps of atmospheric particle formation, their thermochemical data are still not completely available due to limitation of the experimental techniques to treat such small clusters. We have investigated the structures and the thermochemistry of stepwise hydration of clusters containing one bisulfate ion, sulfuric acid, base (ammonia or dimethylamine), and water molecules using quantum chemical methods. We found that water facilitates proton transfer from sulfuric acid or the bisulfate ion to the base or water molecules, and depending on the hydration level, the sulfate ion was formed in most of the base-containing clusters. Read More

Proc Natl Acad Sci U S A 2013 Oct 7;110(43):17223-8. Epub 2013 Oct 7.

Department of Physics, University of Helsinki, 00014 Helsinki, Finland.

Atmospheric aerosols formed by nucleation of vapors affect radiative forcing and therefore climate. However, the underlying mechanisms of nucleation remain unclear, particularly the involvement of organic compounds. Here, we present high-resolution mass spectra of ion clusters observed during new particle formation experiments performed at the Cosmics Leaving Outdoor Droplets chamber at the European Organization for Nuclear Research. Read More

J Phys Chem A 2012 Jan 11;116(3):1030-40. Epub 2012 Jan 11.

Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States.

The structures of positively and negatively charged clusters of sulfuric acid with ammonia and/or dimethylamine ((CH(3))(2)NH or DMA) are investigated using a combination of Monte Carlo configuration sampling, semiempirical calculations, and density functional theory (DFT) calculations. Positively charged clusters of the formula [(NH(4)(+))(x)(HSO(4)(-))(y)](+), where x = y + 1, are studied for 1 ≤ y ≤ 10. These clusters exhibit strong cation-anion interactions, with no contribution to the hydrogen-bonding network from the bisulfate ion protons. Read More