The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Hanna Vehkamaki - One of the best experts on this subject based on the ideXlab platform.
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Free energy barrier in the growth of Sulfuric Acid–ammonia and Sulfuric Acid–dimethylamine clusters
Journal of Chemical Physics, 2013Co-Authors: Tinja Olenius, Ismael K. Ortega, Theo Kurten, Oona Kupiainen-määttä, Hanna VehkamakiAbstract:The first step in atmospheric new particle formation involves the aggregation of gas phase molecules into small molecular clusters that can grow by colliding with gas molecules and each other. In this work we used first principles quantum chemistry combined with a dynamic model to study the steady-state kinetics of sets of small clusters consisting of Sulfuric Acid and ammonia or Sulfuric Acid and dimethylamine molecules. Both sets were studied with and without electrically charged clusters. We show the main clustering pathways in the simulated systems together with the quantum chemical Gibbs free energies of formation of the growing clusters. In the Sulfuric Acid–ammonia system, the major growth pathways exhibit free energy barriers, whereas in the Acid–dimethylamine system the growth occurs mainly via barrierless condensation. When ions are present, charged clusters contribute significantly to the growth in the Acid–ammonia system. For dimethylamine the role of ions is minor, except at very low Acid concentration, and the growing clusters are electrically neutral.
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Linking neutral and charged Sulfuric Acid-ammonia and Sulfuric Acid-dimethylamine clusters
2013Co-Authors: Ismael K. Ortega, Ville Loukonen, Theo Kurten, Oona Kupiainen, Tinja Olenius, Hanna VehkamakiAbstract:We have used a quantum chemical method to calculate the formation free energies of negatively charged Sulfuric Acid - ammonia and Sulfuric Acid - dimethylamine clusters. Using the calculated formation free energies we have estimated the evaporation rates of the clusters. We have compared the evaporation rate of the charged clusters with the corresponding neutral clusters. We found that, although small clusters of Sulfuric Acid with ammonia and dimethylamine are stable and should be present in the atmosphere, they can not be detected using mass spectroscopy techniques. Charging the cluster will result in the fast evaporation of the base molecules, and they will be detected as pure Sulfuric Acid cluster.
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Quantum chemical studies on peroxodiSulfuric Acid-Sulfuric Acid-water clusters
Computational and Theoretical Chemistry, 2011Co-Authors: Martta Toivola, Ismael K. Ortega, Ville Loukonen, Markku R Sundberg, Theo Kurten, Agilio A. H. Pádua, Hanna VehkamakiAbstract:We have applied a multistep quantum chemistry method to study the formation energetics and binding patterns of Sulfuric Acid–peroxodiSulfuric Acid–water clusters, with special focus on the O–O bridge. The length of the O–O bridge correlates linearly with the average length of S–O bonds next to it. The clustering of peroxodiSulfuric Acid with Sulfuric Acid and water is thermodynamically favorable, as is the replacement by peroxodiSulfuric Acid of one (but only one) of the Sulfuric Acid molecules in a Sulfuric Acid–water cluster. However, the presence of H2S2O8 does not enhance the addition of Sulfuric Acid to the clusters.
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The sign preference in Sulfuric Acid nucleation
Journal of Molecular Structure-theochem, 2009Co-Authors: Theo Kurten, Ismael K. Ortega, Hanna VehkamakiAbstract:The binding of Sulfuric Acid to a series of anions and cations of varying chemical complexity is studied using quantum chemical methods. Sulfuric Acid is bound much more strongly to anions than cations, as expected from structural and general chemical considerations, and previous computational studies on charged Sulfuric Acid–water clusters. The results are likely to explain the sign effect observed in atmospheric nucleation phenomena, and indicate that the first steps of ion-induced nucleation are controlled by the specific chemical interactions between the core ion and the condensing molecules rather than by general physical (e.g. electrostatic) effects.
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Structure of Sulfuric Acid–Water Clusters
Nucleation and Atmospheric Aerosols, 2007Co-Authors: Martta Salonen, Ismo Napari, Hanna VehkamakiAbstract:We have studied Sulfuric Acid-water clusters using molecular dynamics method. We have first simulated clusters containing water and undissociated Sulfuric Acid molecules. To explore the influence of molecular dissociation on cluster struc- ture, we have also studied clusters containing water and bisulfate-hydronium ion pairs. Simulations show that Sulfuric Acid tends to lie on the cluster surface whereas bisulfate is inside.
Ismael K. Ortega - One of the best experts on this subject based on the ideXlab platform.
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Free energy barrier in the growth of Sulfuric Acid–ammonia and Sulfuric Acid–dimethylamine clusters
Journal of Chemical Physics, 2013Co-Authors: Tinja Olenius, Ismael K. Ortega, Theo Kurten, Oona Kupiainen-määttä, Hanna VehkamakiAbstract:The first step in atmospheric new particle formation involves the aggregation of gas phase molecules into small molecular clusters that can grow by colliding with gas molecules and each other. In this work we used first principles quantum chemistry combined with a dynamic model to study the steady-state kinetics of sets of small clusters consisting of Sulfuric Acid and ammonia or Sulfuric Acid and dimethylamine molecules. Both sets were studied with and without electrically charged clusters. We show the main clustering pathways in the simulated systems together with the quantum chemical Gibbs free energies of formation of the growing clusters. In the Sulfuric Acid–ammonia system, the major growth pathways exhibit free energy barriers, whereas in the Acid–dimethylamine system the growth occurs mainly via barrierless condensation. When ions are present, charged clusters contribute significantly to the growth in the Acid–ammonia system. For dimethylamine the role of ions is minor, except at very low Acid concentration, and the growing clusters are electrically neutral.
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Linking neutral and charged Sulfuric Acid-ammonia and Sulfuric Acid-dimethylamine clusters
2013Co-Authors: Ismael K. Ortega, Ville Loukonen, Theo Kurten, Oona Kupiainen, Tinja Olenius, Hanna VehkamakiAbstract:We have used a quantum chemical method to calculate the formation free energies of negatively charged Sulfuric Acid - ammonia and Sulfuric Acid - dimethylamine clusters. Using the calculated formation free energies we have estimated the evaporation rates of the clusters. We have compared the evaporation rate of the charged clusters with the corresponding neutral clusters. We found that, although small clusters of Sulfuric Acid with ammonia and dimethylamine are stable and should be present in the atmosphere, they can not be detected using mass spectroscopy techniques. Charging the cluster will result in the fast evaporation of the base molecules, and they will be detected as pure Sulfuric Acid cluster.
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Quantum chemical studies on peroxodiSulfuric Acid-Sulfuric Acid-water clusters
Computational and Theoretical Chemistry, 2011Co-Authors: Martta Toivola, Ismael K. Ortega, Ville Loukonen, Markku R Sundberg, Theo Kurten, Agilio A. H. Pádua, Hanna VehkamakiAbstract:We have applied a multistep quantum chemistry method to study the formation energetics and binding patterns of Sulfuric Acid–peroxodiSulfuric Acid–water clusters, with special focus on the O–O bridge. The length of the O–O bridge correlates linearly with the average length of S–O bonds next to it. The clustering of peroxodiSulfuric Acid with Sulfuric Acid and water is thermodynamically favorable, as is the replacement by peroxodiSulfuric Acid of one (but only one) of the Sulfuric Acid molecules in a Sulfuric Acid–water cluster. However, the presence of H2S2O8 does not enhance the addition of Sulfuric Acid to the clusters.
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The sign preference in Sulfuric Acid nucleation
Journal of Molecular Structure-theochem, 2009Co-Authors: Theo Kurten, Ismael K. Ortega, Hanna VehkamakiAbstract:The binding of Sulfuric Acid to a series of anions and cations of varying chemical complexity is studied using quantum chemical methods. Sulfuric Acid is bound much more strongly to anions than cations, as expected from structural and general chemical considerations, and previous computational studies on charged Sulfuric Acid–water clusters. The results are likely to explain the sign effect observed in atmospheric nucleation phenomena, and indicate that the first steps of ion-induced nucleation are controlled by the specific chemical interactions between the core ion and the condensing molecules rather than by general physical (e.g. electrostatic) effects.
Theo Kurten - One of the best experts on this subject based on the ideXlab platform.
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Free energy barrier in the growth of Sulfuric Acid–ammonia and Sulfuric Acid–dimethylamine clusters
Journal of Chemical Physics, 2013Co-Authors: Tinja Olenius, Ismael K. Ortega, Theo Kurten, Oona Kupiainen-määttä, Hanna VehkamakiAbstract:The first step in atmospheric new particle formation involves the aggregation of gas phase molecules into small molecular clusters that can grow by colliding with gas molecules and each other. In this work we used first principles quantum chemistry combined with a dynamic model to study the steady-state kinetics of sets of small clusters consisting of Sulfuric Acid and ammonia or Sulfuric Acid and dimethylamine molecules. Both sets were studied with and without electrically charged clusters. We show the main clustering pathways in the simulated systems together with the quantum chemical Gibbs free energies of formation of the growing clusters. In the Sulfuric Acid–ammonia system, the major growth pathways exhibit free energy barriers, whereas in the Acid–dimethylamine system the growth occurs mainly via barrierless condensation. When ions are present, charged clusters contribute significantly to the growth in the Acid–ammonia system. For dimethylamine the role of ions is minor, except at very low Acid concentration, and the growing clusters are electrically neutral.
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Linking neutral and charged Sulfuric Acid-ammonia and Sulfuric Acid-dimethylamine clusters
2013Co-Authors: Ismael K. Ortega, Ville Loukonen, Theo Kurten, Oona Kupiainen, Tinja Olenius, Hanna VehkamakiAbstract:We have used a quantum chemical method to calculate the formation free energies of negatively charged Sulfuric Acid - ammonia and Sulfuric Acid - dimethylamine clusters. Using the calculated formation free energies we have estimated the evaporation rates of the clusters. We have compared the evaporation rate of the charged clusters with the corresponding neutral clusters. We found that, although small clusters of Sulfuric Acid with ammonia and dimethylamine are stable and should be present in the atmosphere, they can not be detected using mass spectroscopy techniques. Charging the cluster will result in the fast evaporation of the base molecules, and they will be detected as pure Sulfuric Acid cluster.
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Quantum chemical studies on peroxodiSulfuric Acid-Sulfuric Acid-water clusters
Computational and Theoretical Chemistry, 2011Co-Authors: Martta Toivola, Ismael K. Ortega, Ville Loukonen, Markku R Sundberg, Theo Kurten, Agilio A. H. Pádua, Hanna VehkamakiAbstract:We have applied a multistep quantum chemistry method to study the formation energetics and binding patterns of Sulfuric Acid–peroxodiSulfuric Acid–water clusters, with special focus on the O–O bridge. The length of the O–O bridge correlates linearly with the average length of S–O bonds next to it. The clustering of peroxodiSulfuric Acid with Sulfuric Acid and water is thermodynamically favorable, as is the replacement by peroxodiSulfuric Acid of one (but only one) of the Sulfuric Acid molecules in a Sulfuric Acid–water cluster. However, the presence of H2S2O8 does not enhance the addition of Sulfuric Acid to the clusters.
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The sign preference in Sulfuric Acid nucleation
Journal of Molecular Structure-theochem, 2009Co-Authors: Theo Kurten, Ismael K. Ortega, Hanna VehkamakiAbstract:The binding of Sulfuric Acid to a series of anions and cations of varying chemical complexity is studied using quantum chemical methods. Sulfuric Acid is bound much more strongly to anions than cations, as expected from structural and general chemical considerations, and previous computational studies on charged Sulfuric Acid–water clusters. The results are likely to explain the sign effect observed in atmospheric nucleation phenomena, and indicate that the first steps of ion-induced nucleation are controlled by the specific chemical interactions between the core ion and the condensing molecules rather than by general physical (e.g. electrostatic) effects.
Tinja Olenius - One of the best experts on this subject based on the ideXlab platform.
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Free energy barrier in the growth of Sulfuric Acid–ammonia and Sulfuric Acid–dimethylamine clusters
Journal of Chemical Physics, 2013Co-Authors: Tinja Olenius, Ismael K. Ortega, Theo Kurten, Oona Kupiainen-määttä, Hanna VehkamakiAbstract:The first step in atmospheric new particle formation involves the aggregation of gas phase molecules into small molecular clusters that can grow by colliding with gas molecules and each other. In this work we used first principles quantum chemistry combined with a dynamic model to study the steady-state kinetics of sets of small clusters consisting of Sulfuric Acid and ammonia or Sulfuric Acid and dimethylamine molecules. Both sets were studied with and without electrically charged clusters. We show the main clustering pathways in the simulated systems together with the quantum chemical Gibbs free energies of formation of the growing clusters. In the Sulfuric Acid–ammonia system, the major growth pathways exhibit free energy barriers, whereas in the Acid–dimethylamine system the growth occurs mainly via barrierless condensation. When ions are present, charged clusters contribute significantly to the growth in the Acid–ammonia system. For dimethylamine the role of ions is minor, except at very low Acid concentration, and the growing clusters are electrically neutral.
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Linking neutral and charged Sulfuric Acid-ammonia and Sulfuric Acid-dimethylamine clusters
2013Co-Authors: Ismael K. Ortega, Ville Loukonen, Theo Kurten, Oona Kupiainen, Tinja Olenius, Hanna VehkamakiAbstract:We have used a quantum chemical method to calculate the formation free energies of negatively charged Sulfuric Acid - ammonia and Sulfuric Acid - dimethylamine clusters. Using the calculated formation free energies we have estimated the evaporation rates of the clusters. We have compared the evaporation rate of the charged clusters with the corresponding neutral clusters. We found that, although small clusters of Sulfuric Acid with ammonia and dimethylamine are stable and should be present in the atmosphere, they can not be detected using mass spectroscopy techniques. Charging the cluster will result in the fast evaporation of the base molecules, and they will be detected as pure Sulfuric Acid cluster.
Ville Loukonen - One of the best experts on this subject based on the ideXlab platform.
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Linking neutral and charged Sulfuric Acid-ammonia and Sulfuric Acid-dimethylamine clusters
2013Co-Authors: Ismael K. Ortega, Ville Loukonen, Theo Kurten, Oona Kupiainen, Tinja Olenius, Hanna VehkamakiAbstract:We have used a quantum chemical method to calculate the formation free energies of negatively charged Sulfuric Acid - ammonia and Sulfuric Acid - dimethylamine clusters. Using the calculated formation free energies we have estimated the evaporation rates of the clusters. We have compared the evaporation rate of the charged clusters with the corresponding neutral clusters. We found that, although small clusters of Sulfuric Acid with ammonia and dimethylamine are stable and should be present in the atmosphere, they can not be detected using mass spectroscopy techniques. Charging the cluster will result in the fast evaporation of the base molecules, and they will be detected as pure Sulfuric Acid cluster.
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Quantum chemical studies on peroxodiSulfuric Acid-Sulfuric Acid-water clusters
Computational and Theoretical Chemistry, 2011Co-Authors: Martta Toivola, Ismael K. Ortega, Ville Loukonen, Markku R Sundberg, Theo Kurten, Agilio A. H. Pádua, Hanna VehkamakiAbstract:We have applied a multistep quantum chemistry method to study the formation energetics and binding patterns of Sulfuric Acid–peroxodiSulfuric Acid–water clusters, with special focus on the O–O bridge. The length of the O–O bridge correlates linearly with the average length of S–O bonds next to it. The clustering of peroxodiSulfuric Acid with Sulfuric Acid and water is thermodynamically favorable, as is the replacement by peroxodiSulfuric Acid of one (but only one) of the Sulfuric Acid molecules in a Sulfuric Acid–water cluster. However, the presence of H2S2O8 does not enhance the addition of Sulfuric Acid to the clusters.
