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Bastian B, Asmussen JD, Ben Ltaief L, Czasch A, Jones NC, Hoffmann SV, Pedersen HB, Mudrich M. A new endstation for extreme-ultraviolet spectroscopy of free clusters and nanodroplets. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:075110. [PMID: 35922303 DOI: 10.1063/5.0094430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2022] [Accepted: 06/15/2022] [Indexed: 06/15/2023]
Abstract
In this work, we present a new endstation for the AMOLine of the ASTRID2 synchrotron at Aarhus University, which combines a cluster and nanodroplet beam source with a velocity map imaging and time-of-flight spectrometer for coincidence imaging spectroscopy. Extreme-ultraviolet spectroscopy of free nanoparticles is a powerful tool for studying the photophysics and photochemistry of resonantly excited or ionized nanometer-sized condensed-phase systems. Here, we demonstrate this capability by performing photoelectron-photoion coincidence experiments with pure and doped superfluid helium nanodroplets. Different doping options and beam sources provide a versatile platform to generate various van der Waals clusters as well as He nanodroplets. We present a detailed characterization of the new setup and show examples of its use for measuring high-resolution yield spectra of charged particles, time-of-flight ion mass spectra, anion-cation coincidence spectra, multi-coincidence electron spectra, and angular distributions. A particular focus of the research with this new endstation is on intermolecular charge and energy-transfer processes in heterogeneous nanosystems induced by valence-shell excitation and ionization.
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Affiliation(s)
- Björn Bastian
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
| | - Jakob D Asmussen
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
| | - Ltaief Ben Ltaief
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
| | - Achim Czasch
- Institut für Kernphysik, Goethe Universität, Max-von-Laue-Strasse 1, 60438 Frankfurt, Germany
| | - Nykola C Jones
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
| | - Søren V Hoffmann
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
| | - Henrik B Pedersen
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
| | - Marcel Mudrich
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
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2
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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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3
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Pandey R, Tran S, Zhang J, Yao Y, Kong W. Bimodal velocity and size distributions of pulsed superfluid helium droplet beams. J Chem Phys 2021; 154:134303. [PMID: 33832230 PMCID: PMC8018796 DOI: 10.1063/5.0047158] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Accepted: 03/15/2021] [Indexed: 11/14/2022] Open
Abstract
We report detailed measurements of velocities and sizes of superfluid helium droplets produced from an Even-Lavie pulse valve at stagnation pressures of 20-60 atm and temperatures between 5.7 and 18.0 K. By doping neutral droplets with Rhodamine 6G cations produced from an electrospray ionization source and detecting the positively charged droplets at two different locations along the beam path, we determine the velocities of the different groups of droplets. By subjecting the doped droplet beam to a retardation field, size distributions can then be analyzed. We discover that at stagnation temperatures above 8.0 K, a single group of droplets is observed at both locations, but at 8.0 K and below, two different groups of droplets with different velocities are detectable. The slower group, considered from fragmentation of liquid helium, cannot be deterred by the retardation voltage at 9 kV, implying an exceedingly large size. The faster group, considered from condensation of gaseous helium, has a bimodal distribution when the stagnation temperatures are below 12.3 K at 20 and 40 atm, or 16.1 K at 60 atm. We also report similar size measurements using low energy electrons for impact ionization, and this latter method can be used for facile in situ characterization of pulsed droplet beams. The mechanism of the bimodal size distribution of the condensation group and the reason for the coexistence of both the condensation and fragmentation groups remain elusive.
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Affiliation(s)
- Rahul Pandey
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
| | - Steven Tran
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
| | - Jie Zhang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
| | - Yuzhong Yao
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
| | - Wei Kong
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
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4
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Niman JW, Kamerin BS, Kranabetter L, Merthe DJ, Suchan J, Slavíček P, Kresin VV. Direct detection of polar structure formation in helium nanodroplets by beam deflection measurements. Phys Chem Chem Phys 2019; 21:20764-20769. [PMID: 31513195 DOI: 10.1039/c9cp04322e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Long-range intermolecular forces are able to steer polar molecules submerged in superfluid helium nanodroplets into highly polar metastable configurations. We demonstrate that the presence of such special structures can be identified, in a direct and determinative way, by electrostatic deflection of the doped nanodroplet beam. The measurement also establishes the structures' electric dipole moments. In consequence, the introduced approach is complementary to spectroscopic studies of low-temperature molecular assembly reactions. It is enabled by the fact that within the cold superfluid matrix the molecular dipoles become nearly completely oriented by the applied electric field. As a result, the massive (tens of thousands of helium atoms) nanodroplets undergo significant deflections. The method is illustrated here by an application to dimers and trimers of dimethyl sulfoxide (DMSO) molecules. We interpret the experimental results with ab initio theory, mapping the potential energy surface of DMSO complexes and simulating their low temperature aggregation dynamics.
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Affiliation(s)
- John W Niman
- Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089-0484, USA.
| | - Benjamin S Kamerin
- Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089-0484, USA.
| | - Lorenz Kranabetter
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
| | - Daniel J Merthe
- Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089-0484, USA.
| | - Jiří Suchan
- Department of Physical Chemistry, University of Chemistry and Technology, Technická 5, Prague 6, Czech Republic.
| | - Petr Slavíček
- Department of Physical Chemistry, University of Chemistry and Technology, Technická 5, Prague 6, Czech Republic. and J. Heyrovský Institute of Physical Chemistry v.v.i., The Czech Academy of Sciences, Dolejškova 3, 18223 Prague, Czech Republic
| | - Vitaly V Kresin
- Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089-0484, USA.
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5
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Mahmoodi-Darian M, Lundberg L, Zöttl S, Scheier P, Echt O. Electron Attachment and Electron Ionization of Formic Acid Clusters Embedded in Helium Nanodroplets. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2019; 30:787-795. [PMID: 30805883 PMCID: PMC6502787 DOI: 10.1007/s13361-018-02124-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 12/14/2018] [Accepted: 12/18/2018] [Indexed: 05/18/2023]
Abstract
We report the results of an experimental study of electron ionization of large helium nanodroplets doped with formic acid (FA). Several homologous series of cluster anions are observed, including [FAn-H]-, undissociated FAn-, and these ions complexed with one or more H2O. Some major features resemble those observed upon sputtering of frozen FA films but they differ significantly from results obtained by electron attachment to bare FA clusters in the gas phase. The FAn- and (H2O)[FAn-H]- series show abrupt onsets above n = 2 and 5, respectively. A prominent resonance in the anion yield occurs at 22.5 eV due to the formation of an intermediate He-*. Also observed are homologous series of [FA-H]- or [FA2-H]- complexed with helium. The cation chemistry is dominated by the production of protonated formic acid clusters, [FAnH]+, but various other homologous cluster ion series are observed as well. Graphical Abstract.
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Affiliation(s)
| | - Linnea Lundberg
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020, Innsbruck, Austria
| | - Samuel Zöttl
- 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
| | - Olof Echt
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020, Innsbruck, Austria.
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6
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Gámez F, Pysanenko A, Fárník M, Ončák M. Ionization of carboxylic acid clusters in the gas phase and on free ArN and (H2O)N nanoparticles: valeric acid as a model for small carboxylic acids. Phys Chem Chem Phys 2019; 21:19201-19208. [DOI: 10.1039/c9cp03279g] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In ionized valeric acid clusters, not only the expected proton transfer reaction, but also anhydride formation is observed. Could this be a common motif in the ionization chemistry of small carboxylic acid clusters?
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Affiliation(s)
- Francisco Gámez
- J. Heyrovský Institute of Physical Chemistry
- v.v.i., Czech Academy of Sciences
- Dolejškova 2155/3
- 182 23 Prague
- Czech Republic
| | - Andriy Pysanenko
- J. Heyrovský Institute of Physical Chemistry
- v.v.i., Czech Academy of Sciences
- Dolejškova 2155/3
- 182 23 Prague
- Czech Republic
| | - Michal Fárník
- J. Heyrovský Institute of Physical Chemistry
- v.v.i., Czech Academy of Sciences
- Dolejškova 2155/3
- 182 23 Prague
- Czech Republic
| | - Milan Ončák
- Institut für Ionenphysik und Angewandte Physik
- Universität Innsbruck
- A-6020 Innsbruck
- Austria
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7
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Berholts M, Myllynen H, Kooser K, Itälä E, Granroth S, Levola H, Laksman J, Oghbaiee S, Oostenrijk B, Nõmmiste E, Kukk E. Photofragmentation of gas-phase acetic acid and acetamide clusters in the vacuum ultraviolet region. J Chem Phys 2017; 147:194302. [PMID: 29166118 DOI: 10.1063/1.4999686] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Photofragmentation of gas-phase acetamide and acetic acid clusters produced by a supersonic expansion source has been studied using time-of-flight mass spectrometry and the partial ion yield (PIY) technique combined with tunable vacuum-ultraviolet synchrotron radiation. Appearance energies of the clusters and their fragments were experimentally determined from the PIY measurements. The effect of clusterization conditions on the formation and fragmentation of acetic acid clusters was investigated. Ab initio quantum mechanical calculations were performed on both samples' dimers to find their neutral and ionized geometries as well as proton transfer energy barriers leading to the optimal geometries. In the case of the acetamide dimer, the reaction resulting in the production of ammoniated acetamide was probed, and the geometry of the obtained ion was calculated.
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Affiliation(s)
- Marta Berholts
- Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland
| | - Hanna Myllynen
- Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland
| | - Kuno Kooser
- Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland
| | - Eero Itälä
- Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland
| | - Sari Granroth
- Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland
| | - Helena Levola
- Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland
| | - Joakim Laksman
- European XFEL, Holzkoppel 4, DE-22869 Schenefeld, Germany
| | - Shabnam Oghbaiee
- Division of Synchrotron Radiation Research, Lund University, Box 118, SE-22100 Lund, Sweden
| | - Bart Oostenrijk
- Division of Synchrotron Radiation Research, Lund University, Box 118, SE-22100 Lund, Sweden
| | - Ergo Nõmmiste
- Department of Physics, University of Tartu, EE-50411 Tartu, Estonia
| | - Edwin Kukk
- Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland
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8
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Neustetter M, Jabbour Al Maalouf E, Limão-Vieira P, Denifl S. Fragmentation pathways of tungsten hexacarbonyl clusters upon electron ionization. J Chem Phys 2016; 145:054301. [PMID: 27497555 DOI: 10.1063/1.4959278] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Electron ionization of neat tungsten hexacarbonyl (W(CO)6) clusters has been investigated in a crossed electron-molecular beam experiment coupled with a mass spectrometer system. The molecule is used for nanofabrication processes through electron beam induced deposition and ion beam induced deposition techniques. Positive ion mass spectra of W(CO)6 clusters formed by electron ionization at 70 eV contain the ion series of the type W(CO)n (+) (0 ≤ n ≤ 6) and W2(CO)n (+) (0 ≤ n ≤ 12). In addition, a series of peaks are observed and have been assigned to WC(CO)n (+) (0 ≤ n ≤ 3) and W2C(CO)n (+) (0 ≤ n ≤ 10). A distinct change of relative fragment ion intensity can be observed for clusters compared to the single molecule. The characteristic fragmentation pattern obtained in the mass spectra can be explained by a sequential decay of the ionized organometallic, which is also supported by the study of the clusters when embedded in helium nanodroplets. In addition, appearance energies for the dissociative ionization channels for singly charged ions have been estimated from experimental ion efficiency curves.
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Affiliation(s)
- M Neustetter
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - E Jabbour Al Maalouf
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - P Limão-Vieira
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - S Denifl
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
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9
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Zhang J, Chen L, Freund WM, Kong W. Effective doping of low energy ions into superfluid helium droplets. J Chem Phys 2015; 143:074201. [PMID: 26298127 PMCID: PMC4545055 DOI: 10.1063/1.4928689] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 08/05/2015] [Indexed: 11/14/2022] Open
Abstract
We report a facile method of doping cations from an electrospray ionization (ESI) source into superfluid helium droplets. By decelerating and stopping the ion pulse of reserpine and substance P from an ESI source in the path of the droplet beam, about 10(4) ion-doped droplets (one ion per droplet) can be recorded, corresponding to a pickup efficiency of nearly 1 out of 1000 ions. We attribute the success of this simple approach to the long residence time of the cations in the droplet beam. The resulting size of the doped droplets, on the order of 10(5)/droplet, is measured using deflection and retardation methods. Our method does not require an ion trap in the doping region, which significantly simplifies the experimental setup and procedure for future spectroscopic and diffraction studies.
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Affiliation(s)
- Jie Zhang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Lei Chen
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - William M Freund
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Wei Kong
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
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10
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Poully JC, Vizcaino V, Schwob L, Delaunay R, Kocisek J, Eden S, Chesnel JY, Méry A, Rangama J, Adoui L, Huber B. Formation and Fragmentation of Protonated Molecules after Ionization of Amino Acid and Lactic Acid Clusters by Collision with Ions in the Gas Phase. Chemphyschem 2015; 16:2389-96. [DOI: 10.1002/cphc.201500275] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Indexed: 11/11/2022]
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Tolbatov I, Bartl P, Yurkovich J, Scheier P, Chipman DM, Denifl S, Ptasinska S. Monocarbon cationic cluster yields from N2/CH4 mixtures embedded in He nanodroplets and their calculated binding energies. J Chem Phys 2014; 140:034316. [PMID: 25669388 DOI: 10.1063/1.4861663] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The formation of monocarbon cluster ions has been investigated by electron ionization mass spectrometry of cold helium nanodroplets doped with nitrogen/methane mixtures. Ion yields for two groups of clusters, CHmN2(+) or CHmN4(+), were determined for mixtures with different molecular ratios of CH4. The possible geometrical structures of these clusters were analyzed using electronic structure computations. Little correlation between the ion yields and the associated binding energies has been observed indicating that in most cases kinetic control is more important than thermodynamic control for forming the clusters.
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Affiliation(s)
- Iogann Tolbatov
- Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, USA
| | - Peter Bartl
- Institut für Ionenphysik und Angewandte Physik and Center of Molecular Biosciences Innsbruck, Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria
| | - James Yurkovich
- Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, USA
| | - Paul Scheier
- Institut für Ionenphysik und Angewandte Physik and Center of Molecular Biosciences Innsbruck, Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria
| | - Daniel M Chipman
- Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, USA
| | - Stephan Denifl
- Institut für Ionenphysik und Angewandte Physik and Center of Molecular Biosciences Innsbruck, Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria
| | - Sylwia Ptasinska
- Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, USA
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12
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Houplin J, Amiaud L, Humblot V, Martin I, Matar E, Azria R, Pradier CM, Lafosse A. Selective terminal function modification of SAMs driven by low-energy electrons (0-15 eV). Phys Chem Chem Phys 2013; 15:7220-7. [PMID: 23558312 DOI: 10.1039/c3cp43750g] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Low-energy electron induced degradation of a model self-assembled monolayer (SAM) of acid terminated alkanethiol was studied under ultra-high vacuum (UHV) conditions at room and low (~40 K) temperatures. Low-energy electron induced chemical modifications of 11-mercaptoundecanoic acid (MUA, HS-(CH2)10-COOH) SAMs deposited on gold were probed in situ as a function of the irradiation energy (<11 eV) by combining two complementary techniques: High Resolution Electron Energy Loss Spectroscopy (HREELS), a surface sensitive vibrational spectroscopy technique, and Electron Stimulated Desorption (ESD) analysis of neutral fragments. The SAM's terminal functions were observed to be selectively damaged at around 1 eV by a resonant electron attachment mechanism, observed to decay by CO, CO2 and H2O formation and desorption. CO2 and H2O were also directly identified at low temperature by vibrational analysis of the irradiated SAMs. At higher irradiation energy, both terminal functions and spacer alkyl chains are damaged upon electron irradiation, by resonant and non-resonant processes.
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Affiliation(s)
- J Houplin
- Université Paris-Sud, Institut des Sciences Moléculaires d'Orsay (ISMO), UMR 8214, Orsay, France
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13
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Bartl P, Tanzer K, Mitterdorfer C, Karolczak S, Illenberger E, Denifl S, Scheier P. Electron ionization of different large perfluoroethers embedded in ultracold helium droplets: effective freezing of short-lived decomposition intermediates. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2013; 27:298-304. [PMID: 23239377 DOI: 10.1002/rcm.6459] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Revised: 10/16/2012] [Accepted: 10/30/2012] [Indexed: 05/22/2023]
Abstract
RATIONALE Electron ionization of three perfluoroethers (PFEs), C(6)F(14)O(3), C(8)F(18)O(4), and C(10)F(20)O(5), is studied in the gas phase and when the molecules are embedded in ultracold helium (He) droplets. The molecules investigated are model compounds for perfluoropolyethers used as lubricants in technical applications. The present study gives insight into possible radiolysis pathways upon radiation exposure. METHODS The experiments utilized a crossed electron/droplet beam apparatus consisting of a He droplet source and pick-up chamber combined with a commercial time-of-flight mass spectrometer. The doped droplets were ionized by electron ionization at 70 eV. RESULTS The He environment strongly affects the ionization patterns in the way that both the molecular ion M(+) and high-mass fragment ions formed by the loss of light neutral species such as F([M-F](+)), or CF(3)OCF(2) ([M-CF(3)OCF(2)](+)), etc., became strong signals in the mass spectrum. These signals were not or only barely visible in the gas-phase experiment and were identified as short lived (< µs) dissociation intermediates which in the gas phase immediately decomposed into lower-mass fragment ions. CONCLUSIONS Ionic fragmentation intermediates are frozen and subsequently stabilized in the He environment. Helium droplets can hence be viewed as a cryogenic laboratory transforming short-lived decomposition intermediates into stable fragment ions appearing as strong signals in the mass spectrum.
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Affiliation(s)
- P Bartl
- Institut für Ionenphysik und Angewandte Physik, Leopold Franzens Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
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14
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Ferreira da Silva F, Ptasińska S, Denifl S, Gschliesser D, Postler J, Matias C, Märk TD, Limão-Vieira P, Scheier P. Electron interaction with nitromethane embedded in helium droplets: attachment and ionization measurements. J Chem Phys 2012; 135:174504. [PMID: 22070303 DOI: 10.1063/1.3656680] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Results of a detailed study on electron interactions with nitromethane (CH(3)NO(2)) embedded in helium nanodroplets are reported. Anionic and cationic products formed are analysed by mass spectrometry. When the doped helium droplets are irradiated with low-energy electrons of about 2 eV kinetic energy, exclusively parent cluster anions (CH(3)NO(2))(n)(-) are formed. At 8.5 eV, three anion cluster series are observed, i.e., (CH(3)NO(2))(n)(-), [(CH(3)NO(2))(n)-H](-), and (CH(3)NO(2))(n)NO(2)(-), the latter being the most abundant. The results obtained for anions are compared with previous electron attachment studies with bare nitromethane and nitromethane condensed on a surface. The cation chemistry (induced by electron ionization of the helium matrix at 70 eV and subsequent charge transfer from He(+) to the dopant cluster) is dominated by production of methylated and protonated nitromethane clusters, (CH(3)NO(2))(n)CH(3)(+) and (CH(3)NO(2))(n)H(+).
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Affiliation(s)
- F Ferreira da Silva
- Institut für Ionenphysik und Angewandte Physik and Centre of Molecular Biosciences Innsbruck, Universität Innsbruck, Innsbruck, Austria
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15
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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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Ferreira da Silva F, Denifl S, Märk TD, Ellis AM, Scheier P. Electron attachment to amino acid clusters in helium nanodroplets: Glycine, alanine, and serine. J Chem Phys 2010; 132:214306. [DOI: 10.1063/1.3429743] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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17
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Silva FFD, Denifl S, Märk TD, Doltsinis NL, Ellis AM, Scheier P. Electron Attachment to Formamide Clusters in Helium Nanodroplets. J Phys Chem A 2010; 114:1633-8. [DOI: 10.1021/jp909890h] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- F. Ferreira da Silva
- Institut für Ionenphysik und Angewandte Physik and Center of Molecular Biosciences Innsbruck, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria, Department of Physics, King’s College London, The Strand, London WC2R 2LS, United Kingdom, and Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
| | - S. Denifl
- Institut für Ionenphysik und Angewandte Physik and Center of Molecular Biosciences Innsbruck, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria, Department of Physics, King’s College London, The Strand, London WC2R 2LS, United Kingdom, and Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
| | - T. D. Märk
- Institut für Ionenphysik und Angewandte Physik and Center of Molecular Biosciences Innsbruck, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria, Department of Physics, King’s College London, The Strand, London WC2R 2LS, United Kingdom, and Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
| | - N. L. Doltsinis
- Institut für Ionenphysik und Angewandte Physik and Center of Molecular Biosciences Innsbruck, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria, Department of Physics, King’s College London, The Strand, London WC2R 2LS, United Kingdom, and Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
| | - A. M. Ellis
- Institut für Ionenphysik und Angewandte Physik and Center of Molecular Biosciences Innsbruck, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria, Department of Physics, King’s College London, The Strand, London WC2R 2LS, United Kingdom, and Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
| | - P. Scheier
- Institut für Ionenphysik und Angewandte Physik and Center of Molecular Biosciences Innsbruck, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria, Department of Physics, King’s College London, The Strand, London WC2R 2LS, United Kingdom, and Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
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