| 1. |
- Duensing, Felix, et al.
(author)
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Complexes with Atomic Gold Ions : Efficient Bis-Ligand Formation
- 2021
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In: Molecules. - : MDPI AG. - 1431-5157 .- 1420-3049. ; 26:12
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Journal article (peer-reviewed)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. |
- Gstir, Thomas, et al.
(author)
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Reaction dynamics of the methoxy anion CH3O− with methyl iodide CH3I
- 2024
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In: Faraday discussions. - 1359-6640 .- 1364-5498.
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Journal article (peer-reviewed)abstract
- Studying larger nucleophiles in bimolecular nucleophilic substitution (SN2) reactions bridges the gap from simple model systems to those relevant to organic chemistry. Therefore, we investigated the reaction dynamics between the methoxy anion (CH3O−) and iodomethane (CH3I) in our crossed-beam setup combined with velocity map imaging at the four collision energies 0.4, 0.7, 1.2, and 1.6 eV. We find the two ionic products I− and CH2I−, which can be attributed to the SN2 and proton transfer channels, respectively. The proton transfer channel progresses in a previously observed fashion from indirect to direct scattering with increasing collision energy. Interestingly, the SN2 channel exhibits direct dynamics already at low collision energies. Both the direct stripping, leading to forward scattering, and the direct rebound mechanism, leading to backward scattering into high angles, are observed.
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| 3. |
- Kappe, Miriam, et al.
(author)
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Spectroscopy of helium-tagged C60 anions
- 2024
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In: Physical Review Research. - 2643-1564. ; 6:1
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Journal article (peer-reviewed)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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| 4. |
- Laimer, Felix, et al.
(author)
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Highly Charged Droplets of Superfluid Helium
- 2019
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 123:16
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Journal article (peer-reviewed)abstract
- We report on the production and study of stable, highly charged droplets of superfluid helium. Using a novel experimental setup we produce neutral beams of liquid helium nanodroplets containing millions of atoms or more that can be ionized by electron impact, mass-per-charge selected, and ionized a second time before being analyzed. Droplets containing up to 55 net positive charges are identified and the appearance sizes of multiply charge droplets are determined as a function of the charge state. We show that the droplets are stable on the millisecond timescale of the experiment and decay through the loss of small charged clusters, not through symmetric Coulomb explosions.
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| 5. |
- Laimer, Felix, et al.
(author)
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Multiply Charged Helium Droplet Anions
- 2021
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In: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 27:25, s. 7283-7287
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Journal article (peer-reviewed)abstract
- The detection of multiply charged helium droplet anions is reported for the first time. By ionizing droplets of superfluid helium with low energy electrons (up to 25 eV), it was possible to produce droplets containing up to five negative charges, which remain intact on the timescale of the experiment. The appearance sizes for different charge states are determined and are found to be orders of magnitude larger than for the equivalent cationic droplets, starting at 4 million He atoms for dianions. Droplets with He*(-) as charge carriers show signs of being metastable, but this effect is quenched by the pickup of water molecules.
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| 6. |
- Martini, Paul, et al.
(author)
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Splashing of Large Helium Nanodroplets upon Surface Collisions
- 2021
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 127:26
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Journal article (peer-reviewed)abstract
- In the present work we observe that helium nanodroplets colliding with surfaces can exhibit splashing in a way that is analogous to classical liquids. We use transmission electron microscopy and mass spectrometry to demonstrate that neutral and ionic dopants embedded in the droplets are efficiently backscattered in such events. High abundances of weakly bound He-tagged ions of both polarities indicate a gentle extraction mechanism of these ions from the droplets upon collision with a solid surface. This backscattering process is observed for dopant particles with masses up to 400 kilodaltons, indicating an unexpected mechanism that effectively lowers deposition rates of nanoparticles formed in helium droplets.
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