| 1. |
- Dubernet, M. L., et al.
(författare)
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The virtual atomic and molecular data centre (VAMDC) consortium
- 2016
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 49:7
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Tidskriftsartikel (refereegranskat)abstract
- The Virtual Atomic and Molecular Data Centre (VAMDC) Consortium is a worldwide consortium which federates atomic and molecular databases through an e-science infrastructure and an organisation to support this activity. About 90% of the inter-connected databases handle data that are used for the interpretation of astronomical spectra and for modelling in many fields of astrophysics. Recently the VAMDC Consortium has connected databases from the radiation damage and the plasma communities, as well as promoting the publication of data from Indian institutes. This paper describes how the VAMDC Consortium is organised for the optimal distribution of atomic and molecular data for scientific research. It is noted that the VAMDC Consortium strongly advocates that authors of research papers using data cite the original experimental and theoretical papers as well as the relevant databases.
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| 2. |
- Albert, Damien, et al.
(författare)
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A Decade with VAMDC : Results and Ambitions
- 2020
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Ingår i: Atoms. - : MDPI. - 2218-2004. ; 8:4
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an overview of the current status of the Virtual Atomic and Molecular Data Centre (VAMDC) e-infrastructure, including the current status of the VAMDC-connected (or to be connected) databases, updates on the latest technological development within the infrastructure and a presentation of some application tools that make use of the VAMDC e-infrastructure. We analyse the past 10 years of VAMDC development and operation, and assess their impact both on the field of atomic and molecular (A&M) physics itself and on heterogeneous data management in international cooperation. The highly sophisticated VAMDC infrastructure and the related databases developed over this long term make them a perfect resource of sustainable data for future applications in many fields of research. However, we also discuss the current limitations that prevent VAMDC from becoming the main publishing platform and the main source of A&M data for user communities, and present possible solutions under investigation by the consortium. Several user application examples are presented, illustrating the benefits of VAMDC in current research applications, which often need the A&M data from more than one database. Finally, we present our vision for the future of VAMDC.
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| 3. |
- Denifl, S, et al.
(författare)
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Ionization of doped helium nanodroplets : Complexes of C-60 with water clusters
- 2010
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Ingår i: Journal of Chemical Physics. - : American Institute of Physics. - 0021-9606 .- 1089-7690. ; 132:23, s. 234307-
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Tidskriftsartikel (refereegranskat)abstract
- Water clusters are known to undergo an autoprotonation reaction upon ionization by photons or electron impact, resulting in the formation of (H2O)(n)H3O+. Ejection of OH cannot be quenched by near-threshold ionization; it is only partly quenched when clusters are complexed with inert gas atoms. Mass spectra recorded by electron ionization of water-doped helium droplets show that the helium matrix also fails to quench OH loss. The situation changes drastically when helium droplets are codoped with C-60. Charged C-60-water complexes are predominantly unprotonated; C-60(H2O)(4)(+) and (C-60)(2)(H2O)(4)(+) appear with enhanced abundance. Another intense ion series is due to C-60(H2O)(n)OH+; dehydrogenation is proposed to be initiated by charge transfer between the primary He+ ion and C-60. The resulting electronically excited C-60(+)* leads to the formation of a doubly charged C-60-water complex either via emission of an Auger electron from C-60(+)*, or internal Penning ionization of the attached water complex, followed by charge separation within {C-60(H2O)(n)}(2+). This mechanism would also explain previous observations of dehydrogenation reactions in doped helium droplets. Mass-analyzed ion kinetic energy scans reveal spontaneous (unimolecular) dissociation of C-60(H2O)(n)(+). In addition to the loss of single water molecules, a prominent reaction channel yields bare C-60(+) for sizes n=3, 4, or 6. Ab initio Hartree-Fock calculations for C-60-water complexes reveal negligible charge transfer within neutral complexes. Cationic complexes are well described as water clusters weakly bound to C-60(+). For n=3, 4, or 6, fissionlike desorption of the entire water complex from C-60(H2O)(n)(+) energetically competes with the evaporation of a single water molecule. (C) 2010 American Institute of Physics.
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| 4. |
- Linnartz, H., et al.
(författare)
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C-60(+) as a diffuse interstellar band carrier; a spectroscopic story in 6 acts
- 2020
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Ingår i: Journal of Molecular Spectroscopy. - : Elsevier BV. - 0022-2852 .- 1096-083X. ; 367
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Tidskriftsartikel (refereegranskat)abstract
- In 2019 it was exactly 100 years ago that the first two DIBs, diffuse interstellar bands, were discovered by Mary Lea Heger. Today some 500 + DIBs are known. In numerous observational, modelling and laboratory studies, efforts have been made to identify the carriers of these absorption features that are observed in the light of reddened stars crossing diffuse and translucent clouds. Despite several claims over the years that specific DIBs could be assigned to specific species, not one of these withstood dedicated follow-up studies. An exception is C-60(+). In 2015, Campbell et al. showed that two strong bands, recorded in the laboratory around 960 nm, coincided precisely with known DIBs and in follow-up studies three more matches between C-60(+) transitions and new observational DIB studies were claimed. Over the last four years the evidence for C-60(+) as the first identified DIB carrier - including new laboratory data and Hubble Space Telescope observations - has been accumulating, but not all open issues have been solved yet. This article summarizes 6 spectroscopic achievements that sequentially contributed to what seems to become the first DIB story with a happy end.
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| 5. |
- Martini, P., et al.
(författare)
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Mixed cationic clusters of nitrogen and hydrogen
- 2020
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 152:1
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Tidskriftsartikel (refereegranskat)abstract
- The addition of small impurities, such as a single proton charge carrier, in noble gas clusters has recently been shown to have considerable effects on their geometries and stabilities. Here, we report on a mass spectrometric study of cationic clusters of N-2 molecules and the effects that adding hydrogen, in the form of D-2, has on the systems. Protonated nitrogen clusters formed by the breakup of D-2 are shown to have similar behaviors as protonated rare gas clusters. For larger systems consisting of different mixtures of intact N-2 and D-2, different molecular species are found to be interchangeable sometimes with regard to magic numbers. This is especially true for the (N2)n(D-2)(m)D+ systems with n + m = 17, which is particularly abundant for all measured combinations of n and m.
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| 6. |
- Zöttl, S., et al.
(författare)
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Energy harvesting in doped helium nano-droplets
- 2012
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 388:13, s. 132003-
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Tidskriftsartikel (refereegranskat)abstract
- We report the observation of sequential Penning ionization of dopants by metastable helium atoms in helium nano-droplets resulting in doubly charged ions. Strong charge induced dipole-interaction between the excited helium atom and the target ion provides a high probability for the transfer of the internal energy of the excited helium atom to the dopant ion. This process may also lead subsequently to a Coulomb explosion of molecular or cluster dopants.
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| 7. |
- Feinberg, Alexandra J., et al.
(författare)
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X-ray diffractive imaging of highly ionized helium nanodroplets
- 2022
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Ingår i: Physical Review Research. - 2643-1564. ; 4:2
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Tidskriftsartikel (refereegranskat)abstract
- Finding the lowest energy configuration of N unit charges on a sphere, known as Thomson's problem, is a long-standing query which has only been studied via numerical simulations. We present its physical realization using multiply charged He nanodroplets. The charge positions are determined by x-ray coherent diffractive imaging with Xe as a contrast agent. In neutral droplets, filaments resulting from Xe atoms condensing on quantum vortices are observed. Unique to charged droplets, however, Xe clusters that condense on charges are distributed on the surface in lattice-like structures, introducing He droplets as experimental model systems for the study of Thomson's problem.
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| 8. |
- Lushchikova, O. V., et al.
(författare)
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Structure and formation of copper cluster ions in multiply charged He nanodroplets
- 2023
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 25:12, s. 8463-8471
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Tidskriftsartikel (refereegranskat)abstract
- The structure of cationic and anionic Cu clusters grown in multiply charged superfluid He nanodroplets was investigated using He tagging as a chemical probe. Further, the structure assignment was done based on the magic-numbered ions, representing the most energetically favorable structures. The exact geometry of the cluster and positions of He is verified by calculations. It was found that the structure of the clusters grown in the He droplets is similar to that produced with a laser ablation source and the lowest energy structures predicted by theoretical investigations. The only difference is the structure of the Cu5+, which in our experiments has a twisted-X geometry, rather than a bipyramid or planar half-wheel geometry suggested by previous studies. This might be attributed to the different cluster formation mechanisms, the absence of the Ar-tag and the ultracold environment. It was also found that He tends to bind to partially more electro-negative or positive areas of the anionic or cationic clusters, respectively.
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| 9. |
- Mauracher, Andreas, et al.
(författare)
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Metastable anions of dinitrobenzene : Resonances for electron attachment and kinetic energy release
- 2010
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 133:24, s. 244302-
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Tidskriftsartikel (refereegranskat)abstract
- Attachment of free, low-energy electrons to dinitrobenzene (DNB) in the gas phase leads to DNB− as well as several fragment anions. DNB−, (DNB-H)−, (DNB-NO)−, (DNB-2NO)−, and (DNB-NO2)− are found to undergo metastable (unimolecular) dissociation. A rich pattern of resonances in the yield of these metastable reactions versus electron energy is observed; some resonances are highly isomer-specific. Most metastable reactions are accompanied by large average kinetic energy releases (KER) that range from 0.5 to 1.32 eV, typical of complex rearrangement reactions, but (1,3-DNB-H)− features a resonance with a KER of only 0.06 eV for loss of NO. (1,3-DNB-NO)− offers a rare example of a sequential metastable reaction, namely, loss of NO followed by loss of CO to yield C5H4O− with a large KER of 1.32 eV. The G4(MP2) method is applied to compute adiabatic electron affinities and reaction energies for several of the observed metastable channels
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