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García-Alfonso E, Barranco M, Halberstadt N, Pi M. Time-resolved solvation of alkali ions in superfluid helium nanodroplets. J Chem Phys 2024; 160:164308. [PMID: 38651804 DOI: 10.1063/5.0205951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Accepted: 03/29/2024] [Indexed: 04/25/2024] Open
Abstract
The sinking of alkali cations in superfluid 4He nanodroplets is investigated theoretically using liquid 4He time-dependent density functional theory at zero temperature. The simulations illustrate the dynamics of the buildup of the first solvation shell around the ions. The number of helium atoms in this shell is found to linearly increase with time during the first stages of the dynamics. This points to a Poissonian capture process, as concluded in the work of Albrechtsen et al. on the primary steps of Na+ solvation in helium droplets [Albrechtsen et al., Nature 623, 319 (2023)]. The energy dissipation rate by helium atom ejection is found to be quite similar between all alkalis, the main difference being a larger energy dissipated per atom for the lighter alkalis at the beginning of the dynamics. In addition, the number of helium atoms in the first solvation shell is found to be lower at the end of the dynamics than at equilibrium for both Li+ and Na+, pointing to a kinetic rather than thermodynamical control of the snowball size for small and strongly attractive ions.
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Affiliation(s)
- Ernesto García-Alfonso
- Laboratoire Collisions, Agrégats, Réactivité (LCAR), Université de Toulouse, CNRS, 31062 Toulouse, France
| | - Manuel Barranco
- Departament FQA, Facultat de Física, Universitat de Barcelona, Av. Diagonal 645, 08028 Barcelona, Spain
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Barcelona, Spain
| | - Nadine Halberstadt
- Laboratoire Collisions, Agrégats, Réactivité (LCAR), Université de Toulouse, CNRS, 31062 Toulouse, France
| | - Martí Pi
- Departament FQA, Facultat de Física, Universitat de Barcelona, Av. Diagonal 645, 08028 Barcelona, Spain
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Barcelona, Spain
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2
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Zunzunegui-Bru E, Gruber E, Lázaro T, Bartolomei M, Hernández MI, Campos-Martínez J, González-Lezana T, Bergmeister S, Zappa F, Scheier P, Pérez de Tudela R, Hernández-Rojas J, Bretón J. Observation of Multiple Ordered Solvation Shells in Doped Helium Droplets: The Case of He NCa 2. J Phys Chem Lett 2023; 14:3126-3131. [PMID: 36952614 PMCID: PMC10084467 DOI: 10.1021/acs.jpclett.3c00224] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
In this Letter, we report the experimental detection of likely the largest ordered structure of helium atoms surrounding a monatomic impurity observed to date using a recently developed technique. The mass spectrometry investigation of HeNCa2+ clusters, formed in multiply charged helium nanodroplets, reveals magic numbers at N = 12, 32, 44, and 74. Classical optimization and path integral Monte Carlo calculations suggest the existence of up to four shells surrounding the calcium dication which are closed with well-ordered Mozartkugel-like structures: He12Ca2+ with an icosahedron, the second at He32Ca2+ with a dodecahedron, the third at He44Ca2+ with a larger icosahedron, and finally for He74Ca2+, we find that the outermost He atoms form an icosidodecahedron which contains the other inner shells. We analyze the reasons for the formation of such ordered shells in order to guide the selection of possible candidates to exhibit a similar behavior.
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Affiliation(s)
- Eva Zunzunegui-Bru
- Instituto de Física Fundamental, IFF-CSIC, Serrano 123, Madrid 28006, Spain
| | - Elisabeth Gruber
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, Innsbruck 6020, Austria
| | - Teresa Lázaro
- Instituto de Física Fundamental, IFF-CSIC, Serrano 123, Madrid 28006, Spain
| | | | - Marta I Hernández
- Instituto de Física Fundamental, IFF-CSIC, Serrano 123, Madrid 28006, Spain
| | | | | | - Stefan Bergmeister
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, Innsbruck 6020, Austria
| | - Fabio Zappa
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, Innsbruck 6020, Austria
| | - Paul Scheier
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, Innsbruck 6020, Austria
| | | | - Javier Hernández-Rojas
- Departamento de Física and IUdEA, Universidad de La Laguna, La Laguna, 38205, Tenerife, Spain
| | - José Bretón
- Departamento de Física and IUdEA, Universidad de La Laguna, La Laguna, 38205, Tenerife, Spain
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Solvation of Large Polycyclic Aromatic Hydrocarbons in Helium: Cationic and Anionic Hexabenzocoronene. Molecules 2022; 27:molecules27196764. [PMID: 36235296 PMCID: PMC9573446 DOI: 10.3390/molecules27196764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 10/03/2022] [Accepted: 10/07/2022] [Indexed: 11/24/2022] Open
Abstract
The adsorption of helium on charged hexabenzocoronene (Hbc, C42H18), a planar polycyclic aromatic hydrocarbon (PAH) molecule of D6h symmetry, was investigated by a combination of high-resolution mass spectrometry and classical and quantum computational methods. The ion abundance of HenHbc+ complexes versus size n features prominent local anomalies at n = 14, 38, 68, 82, and a weak one at 26, indicating that for these “magic” sizes, the helium evaporation energies are relatively large. Surprisingly, the mass spectra of anionic HenHbc− complexes feature a different set of anomalies, namely at n = 14, 26, 60, and 62, suggesting that the preferred arrangement of the adsorbate atoms depends on the charge of the substrate. The results of our quantum calculations show that the adsorbate layer grows by successive filling of concentric rings that surround the central benzene ring, which is occupied by one helium atom each on either side of the substrate. The helium atoms are fairly localized in filled rings and they approximately preserve the D6h symmetry of the substrate, but helium atoms in partially filled rings are rather delocalized. The first three rings contain six atoms each; they account for magic numbers at n = 14, 26, and 38. The size of the first ring shrinks as atoms are filled into the second ring, and the position of atoms in the second ring changes from hollow sites to bridge sites as atoms are filled into the third ring. Beyond n = 38, however, the arrangement of helium atoms in the first three rings remains essentially frozen. Presumably, another ring is filled at n = 68 for cations and n = 62 for anions. The calculated structures and energies do not account for the difference between charge states, although they agree with the measurements for the cations and show that the first solvation shell of Hbc± is complete at n = 68. Beyond that size, the adsorbate layer becomes three-dimensional, and the circular arrangement of helium changes to hexagonal.
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Ca + Ions Solvated in Helium Clusters. Molecules 2021; 26:molecules26123642. [PMID: 34203679 PMCID: PMC8232145 DOI: 10.3390/molecules26123642] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 06/04/2021] [Accepted: 06/08/2021] [Indexed: 11/16/2022] Open
Abstract
We present a combined experimental and theoretical investigation on Ca+ ions in helium droplets, HeNCa+. The clusters have been formed in the laboratory by means of electron-impact ionization of Ca-doped helium nanodroplets. Energies and structures of such complexes have been computed using various approaches such as path integral Monte Carlo, diffusion Monte Carlo and basin-hopping methods. The potential energy functions employed in these calculations consist of analytical expressions following an improved Lennard-Jones formula whose parameters are fine-tuned by exploiting ab initio estimations. Ion yields of HeNCa+ -obtained via high-resolution mass spectrometry- generally decrease with N with a more pronounced drop between N=17 and N=25, the computed quantum HeNCa+ evaporation energies resembling this behavior. The analysis of the energies and structures reveals that covering Ca+ with 17 He atoms leads to a cluster with one of the smallest energies per atom. As new atoms are added, they continue to fill the first shell at the expense of reducing its stability, until N=25, which corresponds to the maximum number of atoms in that shell. Behavior of the evaporation energies and radial densities suggests liquid-like cluster structures.
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Jake L, Curotto E. On Diffusion Monte Carlo in spaces with multi-valued maps, boundaries and gradient torsion. Chem Phys Lett 2021. [DOI: 10.1016/j.cplett.2020.138167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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González-Lezana T, Echt O, Gatchell M, Bartolomei M, Campos-Martínez J, Scheier P. Solvation of ions in helium. INT REV PHYS CHEM 2020. [DOI: 10.1080/0144235x.2020.1794585] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Tomás González-Lezana
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas IFF-CSIC, Madrid, Spain
| | - Olof Echt
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
- Department of Physics, University of New Hampshire, Durham, NH, USA
| | - Michael Gatchell
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
- Department of Physics, Stockholm University, Stockholm, Sweden
| | - Massimiliano Bartolomei
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas IFF-CSIC, Madrid, Spain
| | - José Campos-Martínez
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas IFF-CSIC, Madrid, Spain
| | - Paul Scheier
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
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Stringer A, Curotto E. An ergodic measure for Diffusion Monte Carlo ground state wavefunctions: Application to a hydrogen cluster with an isotopic impurity. Chem Phys Lett 2019. [DOI: 10.1016/j.cplett.2019.136728] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Ortiz de Zárate J, Bartolomei M, González-Lezana T, Campos-Martínez J, Hernández MI, Pérez de Tudela R, Hernández-Rojas J, Bretón J, Pirani F, Kranabetter L, Martini P, Kuhn M, Laimer F, Scheier P. Snowball formation for Cs + solvation in molecular hydrogen and deuterium. Phys Chem Chem Phys 2019; 21:15662-15668. [PMID: 31271179 DOI: 10.1039/c9cp02017a] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Interactions of atomic cations with molecular hydrogen are of interest for a wide range of applications in hydrogen technologies. These interactions are fairly strong despite being non-covalent, hence one can ask whether hydrogen molecules would form dense, solid-like, solvation shells around the ion (snowballs) or rather a more weakly bound compound. In this work, the interactions between Cs+ and H2 are studied both experimentally and computationally. Isotopic substitution of H2 by D2 is also investigated. On the one hand, helium nanodroplets doped with cesium and hydrogen or deuterium are ionized by electron impact and the (H2/D2)nCs+ (up to n = 30) clusters formed are identified via mass spectrometry. On the other hand, a new analytical potential energy surface, based on ab initio calculations, is developed and used to study cluster energies and structures by means of classical and quantum-mechanical Monte Carlo methods. The most salient features of the measured ion abundances are remarkably mimicked by the computed evaporation energies, particularly for the clusters composed of deuterium. This result supports the reliability of the present potential energy surface and allows us to recommend its use in related systems. Clusters with either twelve H2 or D2 molecules stand out for their stability and quasi-rigid icosahedral structures. However, the first solvation shell involves thirteen or fourteen molecules for hydrogenated or deuterated clusters, respectively. This shell retains its internal structure when extra molecules are added to the second shell and is nearly solid-like, especially for the deuterated clusters. The role played by three-body induction interactions as well as the rotational degrees of freedom is analyzed and they are found to be significant (up to 15% and 18%, respectively) for the molecules belonging to the first solvation shell.
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Affiliation(s)
- Josu Ortiz de Zárate
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas (IFF-CSIC), Serrano 123, 28006 Madrid, Spain.
| | - Massimiliano Bartolomei
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas (IFF-CSIC), Serrano 123, 28006 Madrid, Spain.
| | - Tomás González-Lezana
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas (IFF-CSIC), Serrano 123, 28006 Madrid, Spain.
| | - José Campos-Martínez
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas (IFF-CSIC), Serrano 123, 28006 Madrid, Spain.
| | - Marta I Hernández
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas (IFF-CSIC), Serrano 123, 28006 Madrid, Spain.
| | | | - Javier Hernández-Rojas
- Departamento de Fsica and IUdEA, Universidad de La Laguna, 38205, La Laguna, Tenerife, Spain
| | - José Bretón
- Departamento de Fsica and IUdEA, Universidad de La Laguna, 38205, La Laguna, Tenerife, Spain
| | - Fernando Pirani
- Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia, Perugia, Italy
| | - Lorenz Kranabetter
- Universität Innsbruck, Institut für Ionenphyisk und Angewandte Physik, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Paul Martini
- Universität Innsbruck, Institut für Ionenphyisk und Angewandte Physik, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Martin Kuhn
- Universität Innsbruck, Institut für Ionenphyisk und Angewandte Physik, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Felix Laimer
- Universität Innsbruck, Institut für Ionenphyisk und Angewandte Physik, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Paul Scheier
- Universität Innsbruck, Institut für Ionenphyisk und Angewandte Physik, Technikerstraße 25, 6020 Innsbruck, Austria
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Ozama E, Adachi S, Takayanagi T, Shiga M. Quantum Simulation Verifies the Stability of an 18-Coordinated Actinium-Helium Complex. Chemistry 2018; 24:12716-12721. [DOI: 10.1002/chem.201802554] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 06/18/2018] [Indexed: 11/10/2022]
Affiliation(s)
- Eiki Ozama
- Department of Chemistry; Saitama University; 255 Shimo-Okubo Sakura-ku Saitama City, Saitama 338-8570 Japan
| | - Sadia Adachi
- Department of Chemistry; Saitama University; 255 Shimo-Okubo Sakura-ku Saitama City, Saitama 338-8570 Japan
| | - Toshiyuki Takayanagi
- Department of Chemistry; Saitama University; 255 Shimo-Okubo Sakura-ku Saitama City, Saitama 338-8570 Japan
| | - Motoyuki Shiga
- Center for Computational Science and E-Systems; Japan Atomic Energy Agency; 148-4, Kashiwanoha, Campus, 178-4 Wakashiba Kashiwa Chiba 277-0871 Japan
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Ancilotto F, Barranco M, Coppens F, Eloranta J, Halberstadt N, Hernando A, Mateo D, Pi M. Density functional theory of doped superfluid liquid helium and nanodroplets. INT REV PHYS CHEM 2017. [DOI: 10.1080/0144235x.2017.1351672] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Francesco Ancilotto
- Dipartimento di Fisica e Astronomia ‘Galileo Galilei’ and CNISM, Università di Padova, Padova, Italy
- CNR-IOM Democritos, Trieste, Italy
| | - Manuel Barranco
- Facultat de Física, Departament FQA, Universitat de Barcelona, Barcelona, Spain
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Barcelona, Spain
- Laboratoire des Collisions, Agrégats et Réactivité, IRSAMC, Université Toulouse 3 and CNRS, Toulouse Cedex 09, France
| | - François Coppens
- Laboratoire des Collisions, Agrégats et Réactivité, IRSAMC, Université Toulouse 3 and CNRS, Toulouse Cedex 09, France
| | - Jussi Eloranta
- Department of Chemistry and Biochemistry, California State University at Northridge, Northridge, CA, USA
| | - Nadine Halberstadt
- Laboratoire des Collisions, Agrégats et Réactivité, IRSAMC, Université Toulouse 3 and CNRS, Toulouse Cedex 09, France
| | - Alberto Hernando
- Social Thermodynamics Applied Research (SThAR), EPFL Innovation Park, Lausanne, Switzerland
| | - David Mateo
- Applied Complexity Group, Singapore University of Technology and Design, Singapore, Singapore
| | - Martí Pi
- Facultat de Física, Departament FQA, Universitat de Barcelona, Barcelona, Spain
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Barcelona, Spain
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Pototschnig JV, Lackner F, Hauser AW, Ernst WE. Rydberg states of alkali atoms on superfluid helium nanodroplets: inside or outside? Phys Chem Chem Phys 2017; 19:14718-14728. [PMID: 28540939 PMCID: PMC5708348 DOI: 10.1039/c7cp02332d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 05/12/2017] [Indexed: 11/28/2022]
Abstract
Electronic excitations of an electron bound to an alkali metal ion inside a droplet of superfluid 4He are computed via a combination of helium density functional theory and the numerical integration of the Schrödinger equation for a single electron in a modified, He density dependent atomic pseudopotential. The application of a spectral method to the radial part of the valence electron wavefunction allows the computation of highly excited Rydberg states. For low principal quantum numbers, the energy required to push the electron outward is larger than the solvation energy of the ion. However, for higher principal quantum numbers the situation is reversed, which suggests the stability of a system where the ion sits inside the droplet while the valence electron orbits the nanodroplet.
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Affiliation(s)
- Johann V. Pototschnig
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ;
| | - Florian Lackner
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ;
| | - Andreas W. Hauser
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ;
| | - Wolfgang E. Ernst
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ;
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Leal A, Zhang X, Barranco M, Cargnoni F, Hernando A, Mateo D, Mella M, Drabbels M, Pi M. Dynamics of photoexcited Ba(+) cations in (4)He nanodroplets. J Chem Phys 2016; 144:094302. [PMID: 26957164 DOI: 10.1063/1.4942850] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
We present a joint experimental and theoretical study on the desolvation of Ba(+) cations in (4)He nanodroplets excited via the 6p ← 6s transition. The experiments reveal an efficient desolvation process yielding mainly bare Ba(+) cations and Ba(+)Hen exciplexes with n = 1 and 2. The speed distributions of the ions are well described by Maxwell-Boltzmann distributions with temperatures ranging from 60 to 178 K depending on the excitation frequency and Ba(+) Hen exciplex size. These results have been analyzed by calculations based on a time-dependent density functional description for the helium droplet combined with classical dynamics for the Ba(+). In agreement with experiment, the calculations reveal the dynamical formation of exciplexes following excitation of the Ba(+) cation. In contrast to experimental observation, the calculations do not reveal desolvation of excited Ba(+) cations or exciplexes, even when relaxation pathways to lower lying states are included.
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Affiliation(s)
- Antonio Leal
- Departament ECM, Facultat de Física, and INUB, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain
| | - Xiaohang Zhang
- Laboratoire de Chimie Physique Moléculaire, Swiss Federal Institute of Technology Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Manuel Barranco
- Departament ECM, Facultat de Física, and INUB, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain
| | - Fausto Cargnoni
- Istituto di Scienze e Tecnologie Molecolari (ISTM), Consiglio Nazionale delle Ricerche, via Golgi 19, 20133 Milano, Italy
| | - Alberto Hernando
- Social Thermodynamics Applied Research (SThAR), EPFL Innovation Park, Bâtiment C, CH-1015 Lausanne, Switzerland
| | - David Mateo
- Department of Chemistry and Biochemistry, California State University at Northridge, Northridge, California 91330, USA
| | - Massimo Mella
- Dipartimento di Scienza ed Alta Tecnologia, Università degli Studi dell'Insubria, via Valleggio 11, 22100 Como, Italy
| | - Marcel Drabbels
- Laboratoire de Chimie Physique Moléculaire, Swiss Federal Institute of Technology Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Martí Pi
- Departament ECM, Facultat de Física, and INUB, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain
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Tarchouna HG, Bonifaci N, Aitken F, Mendoza Luna LG, von Haeften K. Formation of Positively Charged Liquid Helium Clusters in Supercritical Helium and their Solidification upon Compression. J Phys Chem Lett 2015; 6:3036-3040. [PMID: 26267199 DOI: 10.1021/acs.jpclett.5b01159] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Positively charged ions were produced in supercritical helium at temperatures from 6 to 10 K and up to 2 MPa using a corona discharge. Their mobility was measured via current-voltage curves, and the hydrodynamic radius was derived using Stokes law. An initial increase and subsequent decrease of hydrodynamic radius was observed and interpreted in terms of growth, compression and solidification of ion clusters. The mobility was modeled using a van der Waals-type thermodynamic state equation for the ion-in-helium mixed system and a temperature-dependent Millikan-Cunningham factor, describing experimental data both in the Knudsen and the Stokes flow region. Regions of maximum hydrodynamic radius and large compressibility were interpreted as boiling points. These points were modeled over a large range of pressures and found to match the Frenkel line of pure helium up to 0.7 MPa, reflecting similarity of density fluctuations in pure supercritical helium and gas-liquid phase transitions of ionic helium clusters.
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Affiliation(s)
- Hejer Gharbi Tarchouna
- †G2ELab-GreEn-ER, Equipe MDE, 21 avenue des Martyrs, CS 90624, 38031 Grenoble Cedex 1, France
- §Laboratory for Materials, Organization and Properties (LabMOP), Campus Universitaire - El Manar, 2092 Tunis, Tunisia
| | - Nelly Bonifaci
- †G2ELab-GreEn-ER, Equipe MDE, 21 avenue des Martyrs, CS 90624, 38031 Grenoble Cedex 1, France
| | - Frédéric Aitken
- †G2ELab-GreEn-ER, Equipe MDE, 21 avenue des Martyrs, CS 90624, 38031 Grenoble Cedex 1, France
| | - Luis Guillermo Mendoza Luna
- ‡Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
| | - Klaus von Haeften
- ‡Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
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Aitken F, Bonifaci N, Mendoza-Luna LG, von Haeften K. Modelling the mobility of positive ion clusters in normal liquid helium over large pressure ranges. Phys Chem Chem Phys 2015; 17:18535-40. [DOI: 10.1039/c5cp02539g] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Positively charged helium clusters, also called ‘snowballs’, have been investigated within normal liquid helium.
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Affiliation(s)
| | | | | | - Klaus von Haeften
- Department of Physics and Astronomy
- University of Leicester
- Leicester
- UK
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Calvo F. Coating Polycyclic Aromatic Hydrocarbon Cations with Helium Clusters: Snowballs and Slush. J Phys Chem A 2014; 119:5959-70. [DOI: 10.1021/jp510799h] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Florent Calvo
- University of Grenoble Alpes, LIPHY, F-38000 Grenoble, France and
- CNRS, LIPHY, F-38000 Grenoble, France
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16
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Issaoui N, Abdessalem K, Ghalla H, Yaghmour SJ, Calvo F, Oujia B. Theoretical investigation of the relative stability of Na+Hen (n = 2–24) clusters: Many-body versus delocalization effects. J Chem Phys 2014; 141:174316. [DOI: 10.1063/1.4900873] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
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Bartl P, Leidlmair C, Denifl S, Scheier P, Echt O. On the size and structure of helium snowballs formed around charged atoms and clusters of noble gases. J Phys Chem A 2014; 118:8050-9. [PMID: 24128371 PMCID: PMC4166691 DOI: 10.1021/jp406540p] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 09/04/2013] [Indexed: 11/30/2022]
Abstract
Helium nanodroplets doped with argon, krypton, or xenon are ionized by electrons and analyzed in a mass spectrometer. HenNgx(+) ions containing up to seven noble gas (Ng) atoms and dozens of helium atoms are identified; the high resolution of the mass spectrometer combined with advanced data analysis make it possible to unscramble contributions from isotopologues that have the same nominal mass but different numbers of helium or Ng atoms, such as the magic He20(84)Kr2(+) and the isobaric, nonmagic He41(84)Kr(+). Anomalies in these ion abundances reveal particularly stable ions; several intriguing patterns emerge. Perhaps most astounding are the results for HenAr(+), which show evidence for three distinct, solid-like solvation shells containing 12, 20, and 12 helium atoms. This observation runs counter to the common notion that only the first solvation shell is solid-like but agrees with calculations by Galli et al. for HenNa(+) [J. Phys. Chem. A 2011, 115, 7300] that reveal three shells of icosahedral symmetry. HenArx(+) (2 ≤ x ≤ 7) ions appear to be especially stable if they contain a total of n + x = 19 atoms. A sequence of anomalies in the abundance distribution of HenKrx(+) suggests that rings of six helium atoms are inserted into the solvation shell each time a krypton atom is added to the ionic core, from Kr(+) to Kr3(+). Previously reported strong anomalies at He12Kr2(+) and He12Kr3(+) [Kim , J. H.; et al. J. Chem. Phys. 2006, 124, 214301] are attributed to a contamination. Only minor local anomalies appear in the distributions of HenXex(+) (x ≤ 3). The distributions of HenKr(+) and HenXe(+) show strikingly similar, broad features that are absent from the distribution of HenAr(+); differences are tentatively ascribed to the very different fragmentation dynamics of these ions.
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Affiliation(s)
- Peter Bartl
- Institut für Ionenphysik und Angewandte Physik, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - Christian Leidlmair
- Institut für Ionenphysik und Angewandte Physik, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - Stephan Denifl
- Institut für Ionenphysik und Angewandte Physik, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - Paul Scheier
- Institut für Ionenphysik und Angewandte Physik, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - Olof Echt
- Institut für Ionenphysik und Angewandte Physik, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
- Department of Physics, University of New Hampshire, Durham, New Hampshire 03824, United States
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Mella M, Cargnoni F. Exciplexes with Ionic Dopants: Stability, Structure, and Experimental Relevance of M+(2P)4Hen (M = Sr, Ba). J Phys Chem A 2014; 118:6473-83. [DOI: 10.1021/jp5027306] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Massimo Mella
- Dipartimento
di Scienza ed Alta Tecnologia, Università dell’Insubria, via Valleggio 11, 22100 Como, Italy
| | - Fausto Cargnoni
- Istituto di Scienze
e Tecnologie Molecolari (ISTM), Consiglio Nazionale delle Ricerche (CNR), via Golgi 19, 20133 Milano, Italy
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19
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Walewski Ł, Forbert H, Marx D. Solvation of molecules in superfluid helium enhances the “interaction induced localization” effect. J Chem Phys 2014; 140:144305. [DOI: 10.1063/1.4870595] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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20
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Cargnoni F, Ponti A, Mella M. Coinage metal exciplexes with helium atoms: a theoretical study of M*(2L)He(n) (M = Cu, Ag, Au; L = P,D). Phys Chem Chem Phys 2013; 15:18410-23. [PMID: 24072257 DOI: 10.1039/c3cp50250c] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The structure and energetics of exciplexes M*((2)L)He(n) (M = Cu, Ag and Au; L = P and D) in their vibrational ground state are studied by employing diffusion Monte Carlo (DMC). Interaction potentials between the excited coinage metals and He atoms are built using the Diatomics-in-Molecule (DIM) approach and ab initio potential curves for the M((2)L)-He dimers. Extending our previous work [Cargnoni et al., J. Phys. Chem. A, 2011, 115, 7141], we computed the dimer potential for Au in the (2)P and (2)D states, as well for Cu and Ag in the (2)D state, employing basis set superposition error-corrected Configuration Interaction calculations. We found that the (2)Π potential correlating with the (2)P state of Au is substantially less binding than for Ag and Cu, a trend well supported by the M(+) ionic radiuses. Conversely, the interaction potentials between a (n - 1)d(9)ns(2 2)D metal and He present a very weak dependency on M itself or the projection of the angular momentum along the dimer axis. This is due to the screening exerted by the ns(2) electrons on the hole in the (n - 1)d shell. Including the spin-orbit coupling perturbatively in the DIM energy matrix has a major effect on the lowest potential energy surface of the (2)P manifold, the one for Cu allowing the formation of a "belt" of five He atoms while the one for Au being completely repulsive. Conversely, spin-orbit coupling has only a weak effect on the (2)D manifold due to the nearly degenerate nature of the diatomic potentials. Structural and energetic results from DMC have been used to support experimental indications for the formation of metastable exciplexes or the opening of non-radiative depopulation channels in bulk and cold gaseous He.
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Affiliation(s)
- Fausto Cargnoni
- Istituto di Scienze e Tecnologie Molecolari (ISTM), Consiglio Nazionale delle Ricerche, via Golgi 19, 20133 Milano, Italy.
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21
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Mella M, Curotto E. Quantum simulations of the hydrogen molecule on ammonia clusters. J Chem Phys 2013; 139:124319. [PMID: 24089779 DOI: 10.1063/1.4821648] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Mixed ammonia-hydrogen molecule clusters [H2-(NH3)n] have been studied with the aim of exploring the quantitative importance of the H2 quantum motion in defining their structure and energetics. Minimum energy structures have been obtained employing genetic algorithm-based optimization methods in conjunction with accurate pair potentials for NH3-NH3 and H2-NH3. These include both a full 5D potential and a spherically averaged reduced surface mimicking the presence of a para-H2. All the putative global minima for n ≥ 7 are characterized by H2 being adsorbed onto a rhomboidal ammonia tetramer motif formed by two double donor and two double acceptor ammonia molecules. In a few cases, the choice of specific rhombus seems to be directed by the vicinity of an ammonia ad-molecule. Diffusion Monte Carlo simulations on a subset of the species obtained highlighted important quantum effects in defining the H2 surface distribution, often resulting in populating rhomboidal sites different from the global minimum one, and showing a compelling correlation between local geometrical features and the relative stability of surface H2. Clathrate-like species have also been studied and suggested to be metastable over a broad range of conditions if formed.
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Affiliation(s)
- Massimo Mella
- Dipartimento di Scienze ed Alta Tecnologia, Università degli Studi dell'Insubria, via Valleggio 11, 22100 Como, Italy
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Abstract
The most commonly employed diffusion Monte Carlo algorithm and some of its variants afford a way to sample configuration space from a so-called “mixed distribution”, the product of an input trial solution to the Schrödinger equation for the ground state and its unknown exact solution. This mixed distribution is sufficient to compute the ground state energy and other properties represented by operators that commute with the Hamiltonian. These energy-related properties are exact, save for a small bias introduced by the input trial function’s incorrect exchange nodes, the so-called “fixed-node error”. However, properties represented by operators that commute with the position operator are also of interest. When calculated by sampling from the mixed distribution, these properties are much more strongly biased by the input trial function. Our objective is to review methods that allow sampling from the desired “pure” distribution, one that is unbiased except for the exchange node error. Thereby, one accurately calculates physical properties such as the dipole and other electrical moments, electrical response properties of molecules, and particle distribution functions for clusters. We survey the results of calculations that employ pure-sampling methods through what has been published in year 2012. Our review also touches on truly exact sampling methods.
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Affiliation(s)
- Stuart M. Rothstein
- Departments of Chemistry and Physics, Brock University, St. Catharines, ON L2S 3A1, Canada
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Unn-Toc W, Halberstadt N, Meier C, Mella M. Exploring the importance of quantum effects in nucleation: the archetypical Ne(n) case. J Chem Phys 2012; 137:014304. [PMID: 22779645 DOI: 10.1063/1.4730033] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The effect of quantum mechanics (QM) on the details of the nucleation process is explored employing Ne clusters as test cases due to their semi-quantal nature. In particular, we investigate the impact of quantum mechanics on both condensation and dissociation rates in the framework of the microcanonical ensemble. Using both classical trajectories and two semi-quantal approaches (zero point averaged dynamics, ZPAD, and Gaussian-based time dependent Hartree, G-TDH) to model cluster and collision dynamics, we simulate the dissociation and monomer capture for Ne(8) as a function of the cluster internal energy, impact parameter and collision speed. The results for the capture probability P(s)(b) as a function of the impact parameter suggest that classical trajectories always underestimate capture probabilities with respect to ZPAD, albeit at most by 15%-20% in the cases we studied. They also do so in some important situations when using G-TDH. More interestingly, dissociation rates k(diss) are grossly overestimated by classical mechanics, at least by one order of magnitude. We interpret both behaviours as mainly due to the reduced amount of kinetic energy available to a quantum cluster for a chosen total internal energy. We also find that the decrease in monomer dissociation energy due to zero point energy effects plays a key role in defining dissociation rates. In fact, semi-quantal and classical results for k(diss) seem to follow a common "corresponding states" behaviour when the proper definition of internal and dissociation energies are used in a transition state model estimation of the evaporation rate constants.
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Affiliation(s)
- Wesley Unn-Toc
- Laboratoire Collisions Agrégats Réactivité-IRSAMC, Université Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse, France
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An der Lan L, Bartl P, Leidlmair C, Jochum R, Denifl S, Echt O, Scheier P. Solvation of Na+, K+, and their dimers in helium. Chemistry 2012; 18:4411-8. [PMID: 22374575 PMCID: PMC3350777 DOI: 10.1002/chem.201103432] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Indexed: 11/10/2022]
Abstract
Helium atoms bind strongly to alkali cations which, when embedded in liquid helium, form so-called snowballs. Calculations suggest that helium atoms in the first solvation layer of these snowballs form rigid structures and that their number (n) is well defined, especially for the lighter alkalis. However, experiments have so far failed to accurately determine values of n. We present high-resolution mass spectra of Na+Hen, K+Hen, Na2+Hen and K2+Hen, formed by electron ionization of doped helium droplets; the data allow for a critical comparison with several theoretical studies. For sodium and potassium monomers the spectra indicate that the value of n is slightly smaller than calculated. Na2+Hen displays two distinct anomalies at n=2 and n=6, in agreement with theory; dissociation energies derived from experiment closely track theoretical values. K2+Hen distributions are fairly featureless, which also agrees with predictions.
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Affiliation(s)
- Lukas An der Lan
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria
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25
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Leidlmair C, Wang Y, Bartl P, Schöbel H, Denifl S, Probst M, Alcamí M, Martín F, Zettergren H, Hansen K, Echt O, Scheier P. Structures, energetics, and dynamics of helium adsorbed on isolated fullerene ions. PHYSICAL REVIEW LETTERS 2012; 108:076101. [PMID: 22401228 DOI: 10.1103/physrevlett.108.076101] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Indexed: 05/27/2023]
Abstract
Helium adsorbed on C(60)(+) and C(70)(+) exhibits phenomena akin to helium on graphite. Mass spectra suggest that commensurate layers form when all carbon hexagons and pentagons are occupied by one He each, but that the solvation shell does not close until 60 He atoms are adsorbed on C(60)(+), or 62 on C(70)(+). Molecular dynamics simulations of C(60)He(n)(+) at 4 K show that the commensurate phase is solid. Helium added to C(60)He(32)(+) will displace some atoms from pentagonal sites, leading to coexistence of a registered layer of immobile atoms interlaced with a nonregistered layer of mobile atoms.
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Affiliation(s)
- Christian Leidlmair
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
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26
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Mella M. Higher order diffusion Monte Carlo propagators for linear rotors as diffusion on a sphere: development and application to O2@He(n). J Chem Phys 2011; 135:114504. [PMID: 21950868 DOI: 10.1063/1.3639190] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Exploiting the theoretical treatment of particles diffusing on corrugated surfaces and the isomorphism between the "particle on a sphere" and a linear molecule rotation, a new diffusion kernel is introduced to increase the order of diffusion Monte Carlo (DMC) simulations involving linear rotors. Tests carried out on model systems indicate the superior performances of the new rotational diffusion kernel with respect to the simpler alternatives previously employed. In particular, it is evidenced a second order convergence toward exact results with respect to the time step of dynamical correlation functions, a fact that guarantees an identical order for the diffusion part of the DMC projector. The algorithmic advantages afforded by the latter are discussed, especially with respect to the "a posteriori" and "on the fly" extrapolation schemes. As a first application to the new algorithm, the structure and energetics of O(2)@He(n) (n = 1-40) clusters have been studied. This was done to investigate the possible cause of the quenching of the reaction between O(2) and Mg witnessed upon increasing the size of superfluid He droplets used as a solvent. With the simulations on O(2) indicating a strong localization in the cluster core, the behaviour as a function of n is ascribed to the extremely fluxional comportment of Mg@He(n), which dwells far from the droplet center, albeit being solvated, when n is large.
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Affiliation(s)
- Massimo Mella
- Dipartimento di Scienze Chimiche ed Ambientali, Università degli Studi dell'Insubria, via Lucini 3, 22100 Como, Italy.
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Cargnoni F, Mella M. Solubility of Metal Atoms in Helium Droplets: Exploring the Effect of the Well Depth Using the Coinage Metals Cu and Ag. J Phys Chem A 2011; 115:7141-52. [PMID: 21425774 DOI: 10.1021/jp112408d] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - Massimo Mella
- School of Chemistry, Cardiff University, Main Building, CF10 3AT Cardiff, United Kingdom
- Dipartimento di Scienze Chimiche ed Ambientali, Università degli Studi dell’Insubria, via Lucini 3, 22100 Como (I), Italy
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Grandinetti F. Review: gas-phase ion chemistry of the noble gases: recent advances and future perspectives. EUROPEAN JOURNAL OF MASS SPECTROMETRY (CHICHESTER, ENGLAND) 2011; 17:423-463. [PMID: 22173538 DOI: 10.1255/ejms.1151] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
This review article surveys recent experimental and theoretical advances in the gas-phase ion chemistry of the noble gases. Covered issues include the interaction of the noble gases with metal and non-metal cations, the conceivable existence of covalent noble-gas anions, the occurrence of ion-molecule reactions involving singly-charged xenon cations, and the occurrence of bond-forming reactions involving doubly-charged cations. Research themes are also highlighted, that are expected to attract further interest in the future.
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Affiliation(s)
- Felice Grandinetti
- Dipartimento per la Innovazione nei sistemi Biologici, Agroalimentari e Forestali, Università della Tuscia, L.go dell'Università, s.n.c., 01100 Viterbo, Italy.
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