| 1. |
- Duensing, Felix, et al.
(författare)
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Complexes with Atomic Gold Ions : Efficient Bis-Ligand Formation
- 2021
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Ingår i: Molecules. - : MDPI AG. - 1431-5157 .- 1420-3049. ; 26:12
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Tidskriftsartikel (refereegranskat)abstract
- Complexes of atomic gold with a variety of ligands have been formed by passing helium nanodroplets (HNDs) through two pickup cells containing gold vapor and the vapor of another dopant, namely a rare gas, a diatomic molecule (H-2, N-2, O-2, I-2, P-2), or various polyatomic molecules (H2O, CO2, SF6, C6H6, adamantane, imidazole, dicyclopentadiene, and fullerene). The doped HNDs were irradiated by electrons; ensuing cations were identified in a high-resolution mass spectrometer. Anions were detected for benzene, dicyclopentadiene, and fullerene. For most ligands L, the abundance distribution of AuLn+ versus size n displays a remarkable enhancement at n = 2. The propensity towards bis-ligand formation is attributed to the formation of covalent bonds in Au+L2 which adopt a dumbbell structure, L-Au+-L, as previously found for L = Xe and C-60. Another interesting observation is the effect of gold on the degree of ionization-induced intramolecular fragmentation. For most systems gold enhances the fragmentation, i.e., intramolecular fragmentation in AuLn+ is larger than in pure L-n(+). Hydrogen, on the other hand, behaves differently, as intramolecular fragmentation in Au(H-2)(n)(+) is weaker than in pure (H-2)(n)(+) by an order of magnitude.
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| 2. |
- Gatchell, Michael, et al.
(författare)
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Complexes of gold and imidazole formed in helium nanodroplets
- 2018
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 20:11, s. 7739-7745
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Tidskriftsartikel (refereegranskat)abstract
- We have studied complexes of gold atoms and imidazole (C3N2H4, abbreviated Im) produced in helium nanodroplets. Following the ionization of the doped droplets we detect a broad range of different Au(m)Im(n)(+) complexes, however we find that for specific values of m certain n are magic and thus particularly abundant. Our density functional theory calculations indicate that these abundant clusters sizes are partially the result of particularly stable complexes, e.g. AuIm(2)(+), and partially due to a transition in fragmentation patterns from the loss of neutral imidazole molecules for large systems to the loss of neutral gold atoms for smaller systems.
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| 3. |
- Gatchell, Michael, et al.
(författare)
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Magic sizes of cationic and protonated argon clusters
- 2018
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 98:2
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Tidskriftsartikel (refereegranskat)abstract
- There has long been a discrepancy between the size distributions of Ar-n(+) clusters measured by different groups regarding whether or not magic numbers appear at sizes corresponding to the closure of icosahedral (sub-) shells. We show that the previously observed magic cluster size distributions are likely the result of an unresolved ArnH+ component, i.e., from protonated argon clusters. We find that the proton impurity gives cluster geometries that are much closer to those for neutral rare-gas clusters, which are known to form icosahedral structures, than for the pure cationic clusters, explaining why the mass spectra from protonated argon clusters better matches these structural models. Our results thus show that even small impurities, e.g., a single proton, can significantly influence the properties of clusters.
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| 4. |
- Goulart, Marcelo, et al.
(författare)
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The structure of coronene cluster ions inferred from H-2 uptake in the gas phase
- 2017
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 19:41, s. 27968-27973
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Tidskriftsartikel (refereegranskat)abstract
- Mass spectra of helium nanodroplets doped with H-2 and coronene feature anomalies in the ion abundance that reveal anomalies in the energetics of adsorption sites. The coronene monomer ion strongly adsorbs up to n = 38 H-2 molecules indicating a commensurate solvation shell that preserves the D-6h symmetry of the substrate. No such feature is seen in the abundance of the coronene dimer through tetramer complexed with H-2; this observation rules out a vertical columnar structure. Instead we see evidence for a columnar structure in which adjacent coronenes are displaced in parallel, forming terraces that offer additional strong adsorption sites. The experimental value for the number of adsorption sites per terrace, approximately six, barely depends on the number of coronene molecules. The displacement estimated from this number exceeds the value reported in several theoretical studies of the bare, neutral coronene dimer.
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| 5. |
- Martini, Paul, et al.
(författare)
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Atomic Gold Ions Clustered with Noble Gases : Helium, Neon, Argon, Krypton, and Xenon
- 2019
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 123:44, s. 9505-9513
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution mass spectra of helium droplets doped with gold and ionized by electrons reveal HenAu+ cluster ions. Additional doping with heavy noble gases results in NenAu+, ArnAu+, KrnAu+, and XenAu+ cluster ions. The high stability predicted for covalently bonded Ar2Au+, Kr2Au+, and Xe2Au+ is reflected in their relatively high abundance. Surprisingly, the abundance of Ne2Au+, which is predicted to have zero covalent bonding character and no enhanced stability, features a local maximum, too. The predicted size and structure of complete solvation shells surrounding ions with essentially nondirectional bonding depends primarily on the ratio sigma* of the ion-ligand versus the ligand-ligand distance. For Au+ solvated in helium and neon, the ratio sigma* is slightly below 1, favoring icosahedral packing in agreement with a maximum observed in the corresponding abundance distributions at n = 12. HenAu+ appears to adopt two additional solvation shells of I-h symmetry, containing 20 and 12 atoms, respectively. For ArnAu+, with sigma* approximate to 0.67, one would expect a solvation shell of octahedral symmetry, in agreement with an enhanced ion abundance at n = 6. Another anomaly in the ion abundance at Ar9Au+ matches a local maximum in its computed dissociation energy.
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