| 1. |
- Andersson, Patrik U, 1970, et al.
(författare)
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Isotope exchange and structural rearrangements in reactions between size-selected ionic water clusters, H3O+(H2O)n and NH4+(H2O)n, and D2O
- 2008
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Ingår i: Phys.Chem.Chem.Phys. - : Royal Society of Chemistry (RSC). ; 10, s. 6127-6134
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen/deuterium exchange in reactions of H3O+(H2O)n and NH4+(H2O)n (1 n 30) with D2O has been studied experimentally at center-of-mass collisions energies of 0.2 eV. For a given cluster size, the cross-sections for H3O+(H2O)n and NH4+(H2O)n are similar, indicating a structural resemblance and energetics of binding. For protonated pure water clusters, H3O+(H2O)n, reacting with D2O the main H/D exchange mechanism is found to be proton catalyzed. In addition the H/D scrambling becomes close to statistically randomized for the larger clusters. For NH4+(H2O)n clusters reacting with D2O, the main mechanism is a D2O/H2O swap reaction. The lifetimes of H3O+(H2O)n clusters have been estimated using RRKM theory and a plateau in lifetime vs. cluster size is found already at n = 10.
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| 2. |
- Hansen, Klavs, 1958, et al.
(författare)
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Magic numbers and stabilities of heavy water clusters,(D2O)ND+, N = 3 −48
- 2019
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Ingår i: International Journal of Mass Spectrometry. - : Elsevier BV. - 1387-3806. ; 440, s. 14-19
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Tidskriftsartikel (refereegranskat)abstract
- The abundance spectrum of deuterated heavy water clusters has been measured, and relative dissociationenergies were extracted from the abundances. The dissociation energies are similar to those of protonatedlight water clusters, except for a slightly reduced excess stability of the N = 21 cluster relative to the N = 22cluster. The difference is interpreted in terms of the special geometry of the N = 21 cluster. The absenceof a similar effect for N = 28/29 suggests that the stability of the N = 28 cluster is not due to a closed shellstructure
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| 3. |
- Hvelplund, P., et al.
(författare)
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Stability and Structure of Protonated Clusters of Ammonia and Water, H+(NH3)(m) (H2O)(n)
- 2010
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 114:27, s. 7301-7310
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Tidskriftsartikel (refereegranskat)abstract
- Mass spectrometric experiments show that protonated mixed ammonia/water clusters predominant exist in three forms namely H+(NH3)(4)(H2O)(n), H+(NH3)(5)(H2O)(n), and H+(NH3)(6)(H2O)(n) (n = 1-25). For the first two series the collisional activation mass spectra are dominated by loss of water, whereas ions of the latter series preferably lose ammonia. The quantitative characteristics of these observations are reproduced by quantum chemical calculations that also provide insight into the geometrical structures of the clusters. Although the experiments and the calculations agree that clusters with five ammonia are thermodynamically preferred, this does not indicate a rigid tetrahedral structure with one central ammonium covered with an inner solvation shell of four ammonia molecules, with water outside, Instead, water and ammonia have comparable affinities to the binding sites of the first shell, with a preference for ammonia for the first two sites, and water for the last two. The "leftover" ammonia molecules bind equally strong as water molecules to sites in the second shell due to synergistic hydrogen binding. Finally, it is discussed whether the observation of enhanced stability of the H+(NH3)(5)(H2O)(20) in terms of magic numbers and associated geometries may be related to a tetrahedral ammonium core encapsulated in a dodecahedral (H2O)(20) structure, typically found in clathrates.
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| 4. |
- Ryding, Mauritz Johan, 1981
(författare)
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Experimental studies of cluster ions containing water, ammonia, pyridine and bisulphate
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Molecular cluster ions are fascinating subjects of study. Bridging the size gap between molecules and bulk, they often display non-trivial size dependent behaviour and properties. As an example, for some cluster types there are certain sizes that are found in unusually high abundance in a produced cluster distribution, these are referred to as gmagic numbers h. Apart from being interesting in their own right and serving as useful model systems in a number of applications, molecular clusters have a very real and important role in the vast and dynamic system we refer to as the atmosphere. Molecular clusters act as precursors for the formation of atmospheric particles. As such, it is necessary to learn as much as possible about the formation, growth, physical properties and chemistry of these clusters, because the particles they form will ultimately have a large effect on the global climate. This work investigates the properties of some ionic molecular clusters and their gas phase reactions with heavy water and ammonia, and also the effects of collision induced dissociation on air. This is done in cluster beam experiments, using two different experimental setups. The first instrument is a quadrupole-time-of-flight instrument, consisting of an electrospray ion source, a quadrupole mass filter, a collision cell and a time-of-flight mass spectrometer. In this instrument, relative reaction cross sections were measured for H+(H2O)n, H+(NH3)1(H2O)n and H+(pyridine)1.3(H2O)n colliding with D2O; and for H+(H2O)n, H+(pyridine)1.2(H2O)n and H+(NH3)1(pyridine)1(H2O)n colliding with NH3. The results for the reaction H+(pyridine)1(H2O)n + NH3 were used to improve a kinetic model of the atmospheric positive ion composition. Abundance spectra and evaporation patterns were recorded for all clusters. It was found that protonated clusters containing water and pyridine do not have magic numbers in the investigated size range (. 1500 u), unlike clusters consisting of water, pyridine and ammonia. Furthermore the magic numbers of H+(NH3)1(pyridine)1(H2O)n were the same as those recorded for H+(NH3)1(H2O)n. Cluster reactions with D2O proceed through a short-lived reaction complex. The clusters add the heavy water molecule and subsequently lose a D2O, HDO or H2O molecule; the latter two reaction channels are associated with a cluster mass increase of one or two atomic mass units, respectively. The formation of a HDO species in a cluster requires proton mobility, and is known to occur in H+(H2O)n clusters. The reaction channel leading to formation of HDO was not observed for protonated water clusters containing an ammonia or pyridine molecule, which is attributed to the proton being bound in place by the Bronsted base. However, the experiments indicate proton mobility in clusters with two or three pyridine molecules, H+(pyridine)2.3(H2O)n. Quantum chemical calculations suggest that this may be due to transfer of the proton to a water molecule, forming H3O+, or due to proton transfer between the two pyridine molecules along a wire of hydrogen bonds. The second instrument is a double sector instrument, having a magnetic sector, a collision cell and an electrostatic sector. Collision induced dissociation of H+(NH3)m(H2O)n clusters (m = 4.6) indicate that clusters having six NH3 prefer to lose NH3, while clusters with four or five NH3 prefer to lose H2O.
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| 5. |
- Ryding, Mauritz Johan, 1981
(författare)
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Interactions of ionic molecular clusters H+(H2O)n, H+(NH3)1(H2O)n and H+(pyridine)1-3(H2O)n with heavy water in cluster beam experiments
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Molecular cluster ions are fascinating subjects of study. Bridging the size gap between molecules and bulk, they often display non-trivial size dependent behavior and properties. Clusters—apart from being interesting in their own right and serving as useful model system in a number of applications—have a very real and important role in the atmosphere. Clusters acts as precursors for atmospheric particle formation, and as such, any uncertainties regarding clusters have a significant impact on the current estimates of global warming. This work investigates the properties of some ionic molecular clusters: H+(H2O)n, H+(NH3)1(H2O)n and H+(pyridine)1-3(H2O)n, as well as their reactions with gas phase heavy water, D2O. This is done in a cluster beam experiment, using a setup consisting of a quadrupole mass filter, a collision cell, and a time-of-flight mass spectrometer. The relative reaction cross section between the clusters and D2O was investigated; it was found that the pure water clusters and ammonia containing cluster have similar cross sections. Furthermore, the cross sections of the pyridine containing clusters differed from those of the pure water clusters and ammonia containing clusters. However, among the pyridine containing clusters, the reaction cross section depended only on the water content and not on the number of pyridine molecules. Previous studies in the field have concluded that the proton mobility in a cationic pure water cluster is large, leading to a H/D scrambling process during the lifetime of the reaction intermediate formed upon collision of the cluster with D2O. This is seen also in the experiments presented here. However, some of the cluster types investigated—H+(NH3)1(H2O)n and H+(pyridine)1(H2O)n —do not show this behavior. For these clusters, the high proton affinity of the basic molecule leads to the proton being locked in place by the nitrogen atom. Surprisingly, it was found that adding additional pyridine molecules to the latter cluster types negates this effect, thus H+(pyridine)2-3(H2O)n clusters exhibit H/D scrambling just like pure protonated water clusters. Quantum chemical calculations show that for H+(pyridine)2(H2O)4-6 there are stable structures where the proton is found on a water molecule. Although these structures are higher in energy compared to the most stable ones (with the proton situated on a pyridine molecule), the thermodynamical barrier for transferring the proton from a pyridine molecule to a water molecule is likely to decrease with cluster size, thus allowing hydronium containing stable cluster isomers.
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| 6. |
- 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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| 7. |
- Ryding, Mauritz Johan, 1981, et al.
(författare)
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Proton mobility in water clusters
- 2012
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Ingår i: European Journal of Mass Spectrometry. - : SAGE Publications. - 1469-0667 .- 1751-6838. ; 18:2, s. 215-222
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Tidskriftsartikel (refereegranskat)abstract
- Proton mobility in water occurs quickly according to the so-called Grotthuss mechanism. This process and its elementary reaction steps can be studied in great detail by applying suitable mass spectrometric methods to ionic water clusters. Careful choice of suitable core ions in combination with analysis of cluster size trends in hydrogen/deuterium isotope exchange rates allows for detailed insights into fascinating dynamic systems. Analysis of the experiments has been promoted by extensive and systematic quantum chemical model calculations. Detailed low-energy mechanistic pathways for efficient water rearrangement and proton transfer steps, in particular cases along short preformed "wires" of hydrogen bonds, have been identified in consistency with experimental findings.
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| 8. |
- 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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| 9. |
- Ryding, Mauritz Johan, 1981, et al.
(författare)
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X-ray induced fragmentation of size-selected salt cluster-ions stored in an ion trap
- 2014
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Ingår i: RSC Advances. - 2046-2069. ; 4:88, s. 47743-47751
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Tidskriftsartikel (refereegranskat)abstract
- A method for spectroscopic characterization of free ionic clusters and nanoparticles utilizing X-ray synchrotron radiation is presented. We demonstrate that size-selected ammonium bisulphate cluster ions, NH 4+(NH 4HSO4) n, captured in a linear ion trap, exhibit well-defined core-level absorption edges in the reconstructed fragment-ion abundance spectra. In addition to the specific photo-fragmentation pathways observed at the N1s-, O1s- and S2p-edges, dissociation also occurs as a consequence of clusters colliding with helium present as buffer gas in the ion trap. Separate off-beam experiments were conducted to establish the activation kinetics of these collision induced dissociation processes. Furthermore, it is demonstrated that the electrons released upon photoionization of background helium are too few in number to produce multiply charged cluster ions, and thereby induce fragmentation of the salt clusters, to any significant degree. The mechanisms for photon absorption and subsequent cluster fragmentation are analysed and discussed. In addition to its inherent element specificity, the method holds promise for cluster structure elucidation resulting from the sensitivity of the near edge absorption structure to the local chemical environment of the excited atom.
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| 10. |
- 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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