Charged Clusters of C60 and Au or Cu: Evidence for Stable Sizes and Specific Dissociation Channels

Abstract We determine a model of the ionic interactions in RF3 compounds, where R is a rare-earth element in the series from La to Lu, by an analysis of data on the bond length and the vibrational mode frequencies of the PrF3, GdF3 and HoF3 molecular monomers. All RF3 monomers are predicted to have a pyramidal shape, displaying a progressive flattening of the molecular shape in parallel with the lanthanide contraction of the bond length. The vibrational frequencies of all monomers are calculated, the results being in good agreement with the data from infrared studies of matrix-isolated molecules. We also evaluate the geometrical structure and the vibrational spectrum of the La2F6 and Ce2F6 dimers, as a further test of the proposed model. -PACS 36.40.Wa (Charged clusters)

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Amine substitution into sulfuric acid – ammonia clusters

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-3591-2012 ◽

2012 ◽

Vol 12 (8) ◽

pp. 3591-3599 ◽

Cited By ~ 63

Author(s):

O. Kupiainen ◽

I. K. Ortega ◽

T. Kurtén ◽

H. Vehkamäki

Keyword(s):

Sulfuric Acid ◽

Base Substitution ◽

Free Energies ◽

Dynamics Model ◽

Base Exchange ◽

Charged Cluster ◽

Charged Clusters ◽

Evaporation Dynamics ◽

Ammonia Clusters ◽

Positively Charged

Abstract. The substitution of ammonia by dimethylamine in sulfuric acid – ammonia – dimethylamine clusters was studied using a collision and evaporation dynamics model. Quantum chemical formation free energies were computed using B3LYP/CBSB7 for geometries and frequencies and RI-CC2/aug-cc-pV(T+d)Z for electronic energies. We first demonstrate the good performance of our method by a comparison with an experimental study investigating base substitution in positively charged clusters, and then continue by simulating base exchange in neutral clusters, which cannot be measured directly. Collisions of a dimethylamine molecule with an ammonia containing positively charged cluster result in the instantaneous evaporation of an ammonia molecule, while the dimethylamine molecule remains in the cluster. According to our simulations, a similar base exchange can take place in neutral clusters, although the overall process is more complicated. Neutral sulfuric acid – ammonia clusters are significantly less stable than their positively charged counterparts, resulting in a competition between cluster evaporation and base exchange.

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From molecular clusters to nanoparticles: second-generation ion-mediated nucleation model

Atmospheric Chemistry and Physics ◽

10.5194/acp-6-5193-2006 ◽

2006 ◽

Vol 6 (12) ◽

pp. 5193-5211 ◽

Cited By ~ 130

Author(s):

F. Yu

Keyword(s):

Atmospheric Aerosols ◽

Second Generation ◽

Cloud Condensation Nuclei ◽

Size Composition ◽

Galactic Cosmic Rays ◽

Lower Atmosphere ◽

Uncertainty Range ◽

Charged Clusters ◽

Charged Nanoparticles ◽

Ion Mobility Spectra

Abstract. Ions, which are generated in the atmosphere by galactic cosmic rays and other ionization sources, may play an important role in the formation of atmospheric aerosols. In the paper, a new second-generation ion-mediated nucleation (IMN) model is presented. The new model explicitly treats the evaporation of neutral and charged clusters and it describes the evolution of the size spectra and composition of both charged and neutral clusters/particles ranging from small clusters of few molecules to large particles of several micrometers in diameter. Schemes used to calculate the evaporation coefficients for small neutral and charged clusters are consistent with the experimental data within the uncertainty range. The present IMN model, which is size-, composition-, and type-resolved, is a powerful tool for investigating the dominant mechanisms and key parameters controlling the formation and subsequent growth of nanoparticles in the atmosphere. This model can be used to analyze simultaneous measurements of the ion-mobility spectra and particle size distributions, which became available only recently. General features of the spectra for ions smaller than the critical size, size-dependent fractions of charged nanoparticles, and asymmetrical charging of freshly nucleated particles predicted by the new IMN model are consistent with recent measurements. Results obtained using the second generation IMN model, in which the most recent thermodynamic data for neutral and charged H2SO4-H2O clusters were used, suggest that ion-mediated nucleation of H2SO4-H2O can lead to a significant production of new particles in the lower atmosphere (including the boundary layer) under favorable conditions. It has been shown that freshly nucleated particles of few nanometers in size can grow by the condensation of low volatile organic compounds to the size of cloud condensation nuclei. In such cases, the chemical composition of nucleated particles larger than ~10 nm is dominated by organics.

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