| 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. |
- Gatchell, Michael, et al.
(författare)
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Protonated Clusters of Neon and Krypton
- 2019
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Ingår i: Journal of the American Society for Mass Spectrometry. - : American Chemical Society (ACS). - 1044-0305 .- 1879-1123. ; 30:12, s. 2632-2636
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of cationic and protonated clusters of neon and krypton. Recent studies using argon have shown that protonated rare gas clusters can have very different magic sizes than pure, cationic clusters. Here, we find that neon behaves similarly to argon, but that the cationic krypton is more similar to its protonated counterparts than the lighter rare gases are, sharing many of the same magic numbers.
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| 5. |
- Gatchell, Michael, et al.
(författare)
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Spectroscopy of corannulene cations in helium nanodroplets
- 2019
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Ingår i: Faraday discussions. - : Royal Society of Chemistry (RSC). - 1359-6640 .- 1364-5498. ; 217, s. 276-289
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Tidskriftsartikel (refereegranskat)abstract
- Helium tagging in action spectroscopy is an efficient method for measuring the absorption spectra of complex molecular ions with minimal perturbations to the gas phase spectra. We have used superfluid helium nanodroplets doped with corannulene to prepare cations of these molecules complexed with different numbers of He atoms. In total we identify 13 different absorption bands from corannulene cations between 5500 angstrom and 6000 angstrom. The He atoms cause a small, chemically induced redshift of the band positions of the corannulene ion. By studying this effect as a function of the number of solvating atoms we are able to identify the formation of solvation structures that are not visible in the mass spectrum. The solvation features detected using action spectroscopy agree very well with the results of atomistic modeling based on path-integral molecular dynamics simulations. By additionally doping our He droplets with D-2, we produce protonated corannulene ions. The absorption spectrum of these ions differs significantly from the case of the radical cations as the numerous narrow bands are replaced by a broad absorption feature that spans nearly 2000 angstrom in width.
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| 6. |
- Goulart, Marcelo, et al.
(författare)
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The adsorption of helium atoms on small cationic gold clusters
- 2018
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 20:14, s. 9554-9560
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Tidskriftsartikel (refereegranskat)abstract
- Adducts formed between small gold cluster cations and helium atoms are reported for the first time. These binary ions, Aun+Hem, were produced by electron ionization of helium nanodroplets doped with neutral gold clusters and were detected using mass spectrometry. For a given value of n, the distribution of ions as a function of the number of added helium atoms, m, has been recorded. Peaks with anomalously high intensities, corresponding to so-called magic number ions, are identified and interpreted in terms of the geometric structures of the underlying Au-n(+) ions. These features can be accounted for by planar structures for Au-n(+) ions with n <= 7, with the addition of helium having no significant effect on the structures of the underlying gold cluster ions. According to ion mobility studies and some theoretical predictions, a 3-D structure is expected for Au-8(+). However, the findings for Au-8(+) in this work are more consistent with a planar structure.
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| 7. |
- Kappe, Miriam, et al.
(författare)
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Spectroscopy of helium-tagged C60 anions
- 2024
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Ingår i: Physical Review Research. - 2643-1564. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of the electronic absorption spectrum of He -tagged buckminsterfullerene anions, C60-. Using a technique that allows for the efficient tagging of complex molecular anions with He, we achieve atomically resolved action spectra that provide an accurate determination of the gas -phase absorption spectrum in the near -infrared In total we 27 bands between 895 and 1057 nm.
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| 8. |
- Kranabetter, Lorenz, et al.
(författare)
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Considerable matrix shift in the electronic transitions of helium-solvated cesium dimer cation Cs2He+n
- 2019
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 21:45, s. 25362-25368
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the photodissociation of helium-solvated cesium dimer cations using action spectroscopy and quantum chemical calculations. The spectrum of Cs2He+ shows three distinct absorption bands into both bound and dissociative states. Upon solvation with further helium atoms, considerable shifts of the absorption bands are observed, exceeding 0.1 eV (850 cm(-1)) already for Cs2He10+, along with significant broadening. The shifts are highly sensitive to the character of the excited state. Our calculations show that helium atoms adsorb on the ends of Cs-2(+). The shifts are particularly pronounced if the excited state orbitals extend to the area occupied by the helium atoms. In this case, Pauli repulsion leads to a deformation of the excited state orbitals, resulting in the observed blue shift of the transition. Since the position of the weakly bound helium atoms is ill defined, Pauli repulsion also explains the broadening.
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| 9. |
- Lundberg, Linnea, et al.
(författare)
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Hydrogenated Gold Clusters from Helium Nanodroplets : Cluster Ionization and Affinities for Protons and Hydrogen Molecules
- 2019
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Ingår i: Journal of the American Society for Mass Spectrometry. - : American Chemical Society (ACS). - 1044-0305 .- 1879-1123. ; 30:10, s. 1906-1913
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Tidskriftsartikel (refereegranskat)abstract
- We report the mass spectrometric detection of hydrogenated gold clusters ionized by electron transfer and proton transfer. The cations appear after the pickup of hydrogen molecules and gold atoms by helium nanodroplets (HNDs) near zero K and subsequent exposure to electron impact. We focus on the size distributions of the gold cluster cations and their hydrogen content, the electron energy dependence of the ion yield, patterns of hydrogenated gold cluster cation stability, and the presence of magic clusters. Ab initio molecular orbital calculations were performed to provide insight into ionization energies and proton affinities of gold clusters as well as into molecular hydrogen affinities of the ionized and protonated gold cluster cations.
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| 10. |
- 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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