| 1. |
- Ryding, Mauritz Johan, 1981, et al.
(författare)
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Isotope exchange in reactions between D2O and size-selected ionic water clusters containing pyridine, H+(pyridine)m(H2O)n
- 2011
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Ingår i: Physical Chemistry Chemical Physics. ; 13:4, s. 1356-1367
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Tidskriftsartikel (refereegranskat)abstract
- Pyridine contg. water clusters, H+(pyridine)m(H2O)n, have been studied both exptl. by a quadrupole time-of-flight mass spectrometer and by quantum chem. calcns. In the expts., H+(pyridine)m(H2O)n with m = 1-4 and n = 0-80 are obsd. For the cluster distributions obsd., there are no magic nos., neither in the abundance spectra, nor in the evapn. spectra from size selected clusters. Expts. with size-selected clusters H+(pyridine)m(H2O)n, with m = 0-3, reacting with D2O at a center-of-mass energy of 0.1 eV were also performed. The cross-sections for H/D isotope exchange depend mainly on the no. of water mols. in the cluster and not on the no. of pyridine mols. Clusters having only one pyridine mol. undergo D2O/H2O ligand exchange, while H+(pyridine)m(H2O)n, with m = 2, 3, exhibit significant H/D scrambling. These results are rationalized by quantum chem. calcns. (B3LYP and MP2) for H+(pyridine)1(H2O)n and H+(pyridine)2(H2O)n, with n = 1-6. In clusters contg. one pyridine, the water mols. form an interconnected network of hydrogen bonds assocd. with the pyridinium ion via a single hydrogen bond. For clusters contg. two pyridines, the two pyridine mols. are completely sepd. by the water mols., with each pyridine being positioned diametrically opposite within the cluster. In agreement with exptl. observations, these calcns. suggest a "see-saw mechanism" for pendular proton transfer between the two pyridines in H+(pyridine)2(H2O)n clusters. [on SciFinder (R)]
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| 2. |
- Ryding, Mauritz Johan, 1981, et al.
(författare)
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Reactions of H+(pyridine)m(H2O)n and H+(NH3)1(pyridine)m(H2O)n with NH3: experiments and kinetic modelling
- 2012
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 12, s. 2809-2822
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Tidskriftsartikel (refereegranskat)abstract
- Reactions between pyridine containing water cluster ions, H+(pyridine)1(H2O)n, H+(pyridine)2(H2O)n and H+(NH3)1(pyridine)1(H2O)n (n up to 15) with NH3 have been studied experimentally using a quadrupole time-of-flight mass spectrometer. The product ions in the reaction between H+(pyridine)m(H2O)n (m = 1 to 2) and NH3 have been determined for the first time. It is found that the reaction mainly leads to cluster ions of the form H+(NH3)1(pyridine)m(H2O)n-x, with x = 1 or 2 depending on the initial size of the reacting cluster ion. For a given number of water molecules (from 5 to 15) in the cluster ion, rate coefficients are found to be slightly lower than those for protonated pure water clusters reacting with ammonia. The rate coefficients obtained from this study are used in a kinetic cluster ion model under tropospheric conditions. The disagreement between ambient ground level measurements and previous models are discussed in relation to the results from our model and future experimental directions are suggested.
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| 3. |
- Zatula, Alexey, et al.
(författare)
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Proton mobility and stability of water clusters containing the bisulfate anion, HSO4-(H2O)n
- 2011
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 13:29, s. 13287-13294
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Tidskriftsartikel (refereegranskat)abstract
- Bisulfate water clusters, HSO(4)-(H(2)O)(n), have been studied both experimentally by a quadrupole time-of-flight mass spectrometer and by quantum chemical calculations. For the cluster distributions studied, there are some possible "magic number" peaks, although the increase in abundance compared to their neighbours is small. Experiments with size-selected clusters with n = 0-25, reacting with D(2)O at a center-of-mass energy of 0.1 eV, were performed, and it was observed that the rate of hydrogen/deuterium exchange is lower for the smallest clusters (n < 8) than for the larger (n > 11), with a transition taking place in the range n = 8-11. We propose that the protonic defect of the bisulfate ion remains rather stationary unless the degree of hydration reaches a given level. In addition, it was observed that H/D scrambling becomes close to statistically randomized for the larger clusters. Insight into this size dependency was obtained by B3LYP/6-311++G(2d, 2p) calculations for HSO(4)(-)(H(2)O)(n) with n = 0-10. In agreement with experimental observations, these calculations suggest pronounced effectiveness of a "see-saw mechanism" for pendular proton transfer with increasing HSO(4)(-)(H(2)O)(n) cluster size.
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