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Albertini S, Gruber E, Zappa F, Krasnokutski S, Laimer F, Scheier P. Chemistry and physics of dopants embedded in helium droplets. MASS SPECTROMETRY REVIEWS 2022; 41:529-567. [PMID: 33993543 DOI: 10.1002/mas.21699] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 04/20/2021] [Accepted: 04/20/2021] [Indexed: 05/18/2023]
Abstract
Helium droplets represent a cold inert matrix, free of walls with outstanding properties to grow complexes and clusters at conditions that are perfect to simulate cold and dense regions of the interstellar medium. At sub-Kelvin temperatures, barrierless reactions triggered by radicals or ions have been observed and studied by optical spectroscopy and mass spectrometry. The present review summarizes developments of experimental techniques and methods and recent results they enabled.
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Affiliation(s)
- Simon Albertini
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| | - Elisabeth Gruber
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| | - Fabio Zappa
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| | - Serge Krasnokutski
- Laboratory Astrophysics Group of the MPI for Astronomy, University of Jena, Jena, Germany
| | - Felix Laimer
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| | - Paul Scheier
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
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2
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Boltnev RE, Vasiliev MM, Kononov EA, Petrov OF. Formation of solid helical filaments at temperatures of superfluid helium as self-organization phenomena in ultracold dusty plasma. Sci Rep 2019; 9:3261. [PMID: 30824787 PMCID: PMC6397283 DOI: 10.1038/s41598-019-40111-w] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Accepted: 02/07/2019] [Indexed: 12/01/2022] Open
Abstract
A multimodal dusty plasma formed in a positive column of the direct current glow discharge at superfluid helium temperatures has been studied for the first time. Formation of a liquid-like dusty plasma structure occurred after injection of polydisperse cerium oxide particles in the glow discharge. The coupling parameter ~10 determined for the dusty plasma structure corresponds very well to its liquid-like type. The cloud of nanoparticles and non-linear waves within the cloud were observed at T < 2 K. Solid helical filaments with length up to 5 mm, diameter up to 22 μm, total charges ~106е, levitating in the gas discharge at the temperature ~2 K and pressure 4 Pa have been observed for the first time. Analysis of the experimental conditions and the filament composition allows us to conclude that the filaments and nanoclusters were formed due to ion sputtering of dielectric material during the experiments.
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Affiliation(s)
- Roman E Boltnev
- Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow, 125412, Russia. .,Branch of Talrose Institute for Energy Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow region, 142432, Russia. .,Moscow Institute of Physics and Technology, Dolgoprudnyi, Moscow region, 141701, Russia.
| | - Mikhail M Vasiliev
- Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow, 125412, Russia.,Moscow Institute of Physics and Technology, Dolgoprudnyi, Moscow region, 141701, Russia
| | - Evgenii A Kononov
- Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow, 125412, Russia.,Moscow Institute of Physics and Technology, Dolgoprudnyi, Moscow region, 141701, Russia
| | - Oleg F Petrov
- Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow, 125412, Russia.,Moscow Institute of Physics and Technology, Dolgoprudnyi, Moscow region, 141701, Russia
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3
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Fine J, Verma D, Jones CF, Wittig C, Vilesov AF. Formation of He4+via electron impact of helium droplets. J Chem Phys 2018; 148:044302. [DOI: 10.1063/1.5001715] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Jordan Fine
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Deepak Verma
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Curtis F. Jones
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Curt Wittig
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Andrey F. Vilesov
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
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4
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Rodríguez-Cantano R, González-Lezana T, Villarreal P. Path integral Monte Carlo investigations on doped helium clusters. INT REV PHYS CHEM 2016. [DOI: 10.1080/0144235x.2015.1132595] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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5
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Villarreal P, Rodríguez-Cantano R, González-Lezana T, Prosmiti R, Delgado-Barrio G, Gianturco FA. Quantum Features of Anionic Species He*⁻ and He₂*⁻ in Small He(N) Clusters. J Phys Chem A 2015; 119:11574-82. [PMID: 26517581 DOI: 10.1021/acs.jpca.5b08470] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We present variational calculations on systems containing a few boson helium atoms attached to electronically excited atomic and molecular helium anions He*⁻ and He₂*⁻ and characterize their structures and energetics. Previously reported high-level ab initio results [Huber, S. E.; Mauracher, A. Mol. Phys. 2014, 112, 794] to describe the interactions between excited (metastable) anions and a neutral He atom have been employed. For the case of the atomic species He*⁻, the corresponding interaction with He suggests large anharmonicity effects due to the presence of a deep well of ∼17,500 cm⁻¹ at short distances, together with a more external shallow secondary well of ∼4 cm⁻¹, both supporting bound levels. Moreover, when a sum of pairwise interactions is assumed to describe the full PES corresponding to the presence of several neutral He atoms, geometrical constraints already predict the complete solvation of the anionic impurity by six helium atoms, giving rise to a bipyramidal structure. In turn, for the anisotropic weak interaction He-He₂*⁻, where the anionic dimer is considered as a rigid rotor, the obtained structures show the tendency of the helium atoms to pack themselves together and largely far away from the dopant, thereby confirming the heliophobic character of He₂*⁻.
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Affiliation(s)
- Pablo Villarreal
- Instituto de Fı́sica Fundamental, IFF-CSIC , Serrano 123, 28006 Madrid, Spain
| | | | | | - Rita Prosmiti
- Instituto de Fı́sica Fundamental, IFF-CSIC , Serrano 123, 28006 Madrid, Spain
| | | | - Franco A Gianturco
- Institute of Ion Physics, The University of Innsbruck , Technikerstrasse 25, 6020 Innsbruck, Austria.,Scuola Normale Superiore ,Piazza dei Cavalieri 7, 56126 Pisa, Italy
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6
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Renzler M, Daxner M, Weinberger N, Denifl S, Scheier P, Echt O. On subthreshold ionization of helium droplets, ejection of He(+), and the role of anions. Phys Chem Chem Phys 2015; 16:22466-70. [PMID: 25230760 DOI: 10.1039/c4cp03236e] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The mechanism of ionization of helium droplets has been investigated in numerous reports but one observation has not found a satisfactory explanation: How are He(+) ions formed and ejected from undoped droplets at electron energies below the ionization threshold of the free atom? Does this path exist at all? A measurement of the ion yields of He(+) and He2(+) as a function of electron energy, electron emission current, and droplet size reveals that metastable He*(-) anions play a crucial role in the formation of free He(+) at subthreshold energies. The proposed model is testable.
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Affiliation(s)
- Michael Renzler
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria.
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Harnisch M, Weinberger N, Denifl S, Scheier P, Echt O. Helium Droplets Doped with Sulfur and C 60. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2015; 119:10919-10924. [PMID: 26045732 PMCID: PMC4450369 DOI: 10.1021/jp510870x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 12/23/2014] [Indexed: 05/29/2023]
Abstract
Clusters of sulfur are grown by passing superfluid helium nanodroplets through a pickup cell filled with sulfur vapor. In some experiments the droplets are codoped with C60. The doped droplets are collided with energetic electrons and the abundance distributions of positively and negatively charged cluster ions are recorded. We report, specifically, distributions of S m+, S m-, and C60S m- containing up to 41 sulfur atoms. We also observe complexes of sulfur cluster anions with helium; distributions are presented for He n S m- with n ≤ 31 and m ≤ 3. The similarity between anionic and cationic C60S m± spectra is in striking contrast to the large differences between spectra of S m+ and S m-.
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Affiliation(s)
- Martina Harnisch
- Institut
für Ionenphysik und Angewandte Physik, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - Nikolaus Weinberger
- 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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8
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Rodríguez-Cantano R, González-Lezana T, Villarreal P, Gianturco FA. A configurational study of helium clusters doped with He∗− and He2∗−. J Chem Phys 2015; 142:104303. [DOI: 10.1063/1.4913958] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Affiliation(s)
| | | | - Pablo Villarreal
- Instituto de Física Fundamental, CSIC, Serrano 123, 28006 Madrid, Spain
| | - Franco A. Gianturco
- Institute of Ion Physics, The University of Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austriaand Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
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9
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Mauracher A, Daxner M, Huber SE, Postler J, Renzler M, Denifl S, Scheier P, Ellis AM. The interaction of He− with fullerenes. J Chem Phys 2015; 142:104306. [DOI: 10.1063/1.4913956] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Andreas Mauracher
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
| | - Matthias Daxner
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
| | - Stefan E. Huber
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
| | - Johannes Postler
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
| | - Michael Renzler
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
| | - Stephan Denifl
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
| | - Paul Scheier
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
| | - Andrew M. Ellis
- Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
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10
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Mauracher A, Daxner M, Postler J, Huber S, Denifl S, Scheier P, Toennies JP. Detection of Negative Charge Carriers in Superfluid Helium Droplets: The Metastable Anions He *- and He 2*-. J Phys Chem Lett 2014; 5:2444-2449. [PMID: 25068008 PMCID: PMC4106244 DOI: 10.1021/jz500917z] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Accepted: 06/20/2014] [Indexed: 05/13/2023]
Abstract
Helium droplets provide the possibility to study phenomena at the very low temperatures at which quantum mechanical effects are more pronounced and fewer quantum states have significant occupation probabilities. Understanding the migration of either positive or negative charges in liquid helium is essential to comprehend charge-induced processes in molecular systems embedded in helium droplets. Here, we report the resonant formation of excited metastable atomic and molecular helium anions in superfluid helium droplets upon electron impact. Although the molecular anion is heliophobic and migrates toward the surface of the helium droplet, the excited metastable atomic helium anion is bound within the helium droplet and exhibits high mobility. The atomic anion is shown to be responsible for the formation of molecular dopant anions upon charge transfer and thus, we clarify the nature of the previously unidentified fast exotic negative charge carrier found in bulk liquid helium.
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Affiliation(s)
- Andreas Mauracher
- Institut
für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25/3, A-6020 Innsbruck, Austria
| | - Matthias Daxner
- Institut
für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25/3, A-6020 Innsbruck, Austria
| | - Johannes Postler
- Institut
für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25/3, A-6020 Innsbruck, Austria
| | - Stefan
E. Huber
- Institut
für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25/3, A-6020 Innsbruck, Austria
| | - Stephan Denifl
- Institut
für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25/3, A-6020 Innsbruck, Austria
| | - Paul Scheier
- Institut
für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25/3, A-6020 Innsbruck, Austria
- P. Scheier. E-mail: . Phone: +43 512 507 52260. Fax: +43 512 507
2922
| | - J. Peter Toennies
- Max
Planck Institut für Dynamik und Selbstorganisation, Am Fassberg 17, D-37077 Göttingen, Germany
- J. P. Toennies.
E-mail: . Phone: +49 551 5176
600.
Fax: +49 551 5176 575
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11
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Huber SE, Mauracher A. On the formation of (anionic) excited helium dimers in helium droplets. J Phys Chem A 2014; 118:6642-7. [PMID: 24866535 PMCID: PMC4141897 DOI: 10.1021/jp503643r] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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Metastable atomic and molecular helium
anions exhibiting high-spin
quartet configurations can be produced in helium droplets via electron
impact. Their lifetimes allow detection in mass spectrometric experiments.
Formation of atomic helium anions comprises collision-induced excitation
of ground state helium and concomitant electron capture. Yet the formation
of molecular helium anions in helium droplets has been an unresolved
issue. In this work, we explore the interaction of excited helium
atoms exhibiting high-spin triplet configurations with ground state
helium using the equation-of-motion coupled-cluster method. Transition
barriers in the energetically lowest He*–He and He*––He interaction potentials prevent molecule formation at the
extremely low temperatures present in helium droplets. In contrast,
some excited states allow a barrier-free formation of molecular helium
(anions). Moreover, we show that the necessary excitation energies
pinpoint (higher) resonances in recently recorded mass spectra and
emend the assignment of those resonances that have previously been
assigned to electron-impact ionization of ground state helium necessitating
subsequent double-electron capture. Embedding molecules or molecular
clusters in helium droplets is a predestined experimental technique
for the study of phenomena at very low temperatures. Profound knowledge
about active processes in the helium environment is required for a
proper assessment of experimental data.
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Affiliation(s)
- Stefan E Huber
- Institut für Ionenphysik und Angewandte Physik, Leopold-Franzens-Universität Innsbruck , Technikerstraße 25, A-6020 Innsbruck, Austria
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12
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Postler J, Vizcaino V, Denifl S, Zappa F, Ralser S, Daxner M, Illenberger E, Scheier P. Electron attachment to CO2 embedded in superfluid He droplets. J Phys Chem A 2014; 118:6553-9. [PMID: 24818738 PMCID: PMC4141896 DOI: 10.1021/jp503179d] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
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Electron attachment to CO2 embedded in superfluid He
droplets leads to ionic complexes of the form (CO2)n– and (CO2)nO– and, at much lower intensities,
He containing ions of the form Hem(CO2)nO–. At low
energies (<5 eV), predominantly the non-decomposed complexes (CO2)n– are formed
via two resonance contributions, similar to electron attachment to
pristine CO2 clusters. The significantly different shapes
and relative resonance positions, however, indicate particular quenching
and mediation processes in CO2@He. A series of further
resonances in the energy range up to 67 eV can be assigned to electronic
excitation of He and capture of the inelastically scattered electron
generating (CO2)n– and two additional processes where an intermediately formed He*
leads to the nonstoichiometric anions (CO2)nO–.
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Affiliation(s)
- Johannes Postler
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck , Technikerstrasse 25, A-6020 Innsbruck, Austria
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