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Potapov A, McCoustra M. Physics and chemistry on the surface of cosmic dust grains: a laboratory view. INT REV PHYS CHEM 2021. [DOI: 10.1080/0144235x.2021.1918498] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Alexey Potapov
- Laboratory Astrophysics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena, Jena, Germany
| | - Martin McCoustra
- Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, UK
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Stubbing JW, McCoustra MRS, Brown WA. A new technique for determining the refractive index of ices at cryogenic temperatures. Phys Chem Chem Phys 2020; 22:25353-25365. [PMID: 33140768 DOI: 10.1039/d0cp02373f] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A reflection-absorption optical (RAO) spectrometer, operating across the ultra-violet/visible (UV/visible) wavelength region, has been developed that allows simultaneous measurements of optical properties and thickness of thin solid films at cryogenic temperatures in ultrahigh vacuum. The RAO spectrometer enables such measurements to be made after ice deposition, as opposed to most current approaches which make measurements during deposition. This allows changes in the optical properties and in the thickness of the film to be determined subsequent to thermal, photon or charged particle processing. This is not possible with current techniques. A data analysis method is presented that allows the wavelength dependent n and k values for ices to be extracted from the reflection-absorption spectra. The validity of this analysis method is shown using model data from the literature. New data are presented for the reflection UV/visible spectra of amorphous and crystalline single component ices of benzene, methyl formate and water adsorbed on a graphite surface. These data show that, for benzene and methyl formate, the crystalline ice has a larger refractive index than amorphous ice, reflecting changes in the electronic environment occurring in the ice during crystallisation. For water, the refractive index does not vary with ice phase.
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Affiliation(s)
- James W Stubbing
- Department of Chemistry, School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QJ, UK.
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Salter TL, Stubbing JW, Brigham L, Brown WA. A TPD and RAIRS comparison of the low temperature surface behavior of benzene, toluene, and xylene on graphite. J Chem Phys 2018; 149:164705. [DOI: 10.1063/1.5051134] [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)
- Tara L. Salter
- Department of Chemistry, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QJ, United Kingdom
| | - James W. Stubbing
- Department of Chemistry, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QJ, United Kingdom
| | - Lorna Brigham
- Department of Chemistry, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QJ, United Kingdom
| | - Wendy A. Brown
- Department of Chemistry, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QJ, United Kingdom
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Stubbing JW, Salter TL, Brown WA, Taj S, McCoustra MRS. A fibre-coupled UHV-compatible variable angle reflection-absorption UV/visible spectrometer. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:054102. [PMID: 29864813 DOI: 10.1063/1.5025405] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We present a novel UV/visible reflection-absorption spectrometer for determining the refractive index, n, and thicknesses, d, of ice films. Knowledge of the refractive index of these films is of particular relevance to the astrochemical community, where they can be used to model radiative transfer and spectra of various regions of space. In order to make these models more accurate, values of n need to be recorded under astronomically relevant conditions, that is, under ultra-high vacuum (UHV) and cryogenic cooling. Several design considerations were taken into account to allow UHV compatibility combined with ease of use. The key design feature is a stainless steel rhombus coupled to an external linear drive (z-shift) allowing a variable reflection geometry to be achieved, which is necessary for our analysis. Test data for amorphous benzene ice are presented as a proof of concept, the film thickness, d, was found to vary linearly with surface exposure, and a value for n of 1.43 ± 0.07 was determined.
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Affiliation(s)
- J W Stubbing
- Department of Chemistry, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QJ, United Kingdom
| | - T L Salter
- Department of Chemistry, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QJ, United Kingdom
| | - W A Brown
- Department of Chemistry, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QJ, United Kingdom
| | - S Taj
- Institute of Chemical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom
| | - M R S McCoustra
- Institute of Chemical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom
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5
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Michoulier E, Ben Amor N, Rapacioli M, Noble JA, Mascetti J, Toubin C, Simon A. Theoretical determination of adsorption and ionisation energies of polycyclic aromatic hydrocarbons on water ice. Phys Chem Chem Phys 2018; 20:11941-11953. [PMID: 29667677 DOI: 10.1039/c8cp01175c] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In dense interstellar environments, Polycyclic Aromatic Hydrocarbons (PAHs) are likely to condense onto or integrate into water ice mantles covering dust grains. Understanding the role of ice in the photo-induced processes involving adsorbed PAHs is therefore a key issue in astrochemistry. This requires (i) the knowledge of PAH-ice interactions, i.e. PAH-ice adsorption energies and local structures at the PAH-ice interface, as well as (ii) the understanding of the fate of electrons in the PAH-ice system upon excitation. Regarding (i), in this work, we determined the lowest energy structures of PAH-ice systems for a variety of PAHs ranging from naphthalene to ovalene on three types of ice - crystalline (Ih and Ic) and amorphous (low density) - using an explicit description of the electrons and a finite-sized system. The electronic structure was determined using the Self Consistent Charge Density Functional based Tight Binding (SCC-DFTB) scheme with modified Mulliken charges in order to ensure a good description of the studied systems. Regarding (ii), the influence of the interaction with ice on the Vertical Ionisation Potentials (VIPs) of the series of PAHs was determined using the constrained SCC-DFTB scheme benchmarked against correlated wavefunction results for PAH-(H2O)n (n = 1-6, 13) clusters. The results show a deviation equal, at most, to ∼1.4 eV of the VIPs of PAHs adsorbed on ice with respect to the gas phase values. Our results are discussed in the light of experimental data and previous theoretical studies.
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Affiliation(s)
- Eric Michoulier
- Lab. Chim. & Phys. Quant. LCPQ IRSAMC, Univ. Toulouse [UPS] UPS & CNRS, UMR5626, 118 Route Narbonne, F-31062, Toulouse, France.
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Dawes A, Pascual N, Mason NJ, Gärtner S, Hoffmann SV, Jones NC. Probing the interaction between solid benzene and water using vacuum ultraviolet and infrared spectroscopy. Phys Chem Chem Phys 2018; 20:15273-15287. [DOI: 10.1039/c8cp01228h] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Benzene exhibits strong concentration dependent energy shifts of electronic states in solid phase mixtures with water ice.
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Affiliation(s)
- Anita Dawes
- School of Physical Sciences
- The Open University
- Walton Hall
- Milton Keynes
- UK
| | - Natalia Pascual
- Department of Chemistry and Physics
- La Trobe Institute for Molecular Science
- La Trobe University
- Melbourne 3086
- Australia
| | - Nigel J. Mason
- School of Physical Sciences
- The Open University
- Walton Hall
- Milton Keynes
- UK
| | - Sabrina Gärtner
- ISIS Neutron and Muon Source
- Science and Technology Facilities Council
- Rutherford Appleton Laboratory
- Didcot
- UK
| | - Søren V. Hoffmann
- ISA
- Centre for Storage Ring Facilities
- Department of Physics and Astronomy
- Aarhus University
- DK-8000 Aarhus C
| | - Nykola C. Jones
- ISA
- Centre for Storage Ring Facilities
- Department of Physics and Astronomy
- Aarhus University
- DK-8000 Aarhus C
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Michoulier E, Noble JA, Simon A, Mascetti J, Toubin C. Adsorption of PAHs on interstellar ice viewed by classical molecular dynamics. Phys Chem Chem Phys 2018. [DOI: 10.1039/c8cp00593a] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The present work represents a complete description of PAH–ice interaction in the ground electronic state and at low temperature, providing the binding energies and barrier heights necessary to the ongoing improvement of astrochemical models.
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Affiliation(s)
- Eric Michoulier
- Laboratoire de Physique des Lasers
- Atomes et Molécules (PhLAM) UMR 8523 CNRS
- Université de Lille
- France
| | - Jennifer A. Noble
- Laboratoire de Physique des Lasers
- Atomes et Molécules (PhLAM) UMR 8523 CNRS
- Université de Lille
- France
- Institut des Sciences Moléculaires (ISM) – UMR 5255 CNRS
| | - Aude Simon
- Laboratoire de Chimie et Physique Quantiques (LCPQ) – IRSAMC UMR 5626 CNRS
- Université de Toulouse
- France
| | - Joëlle Mascetti
- Laboratoire de Chimie et Physique Quantiques (LCPQ) – IRSAMC UMR 5626 CNRS
- Université de Toulouse
- France
| | - Céline Toubin
- Laboratoire de Physique des Lasers
- Atomes et Molécules (PhLAM) UMR 8523 CNRS
- Université de Lille
- France
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Gadallah KAK, Marchione D, Koehler SPK, McCoustra MRS. Molecular hydrogen production from amorphous solid water during low energy electron irradiation. Phys Chem Chem Phys 2017; 19:3349-3357. [PMID: 28091646 DOI: 10.1039/c6cp06928b] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This work investigates the production of molecular hydrogen isotopologues (H2, HD, and D2) during low energy electron irradiation of layered and isotopically labelled thin films of amorphous solid water (ASW) in ultrahigh vacuum. Experimentally, the production of these molecules with both irradiation time and incident electron energy in the range 400 to 500 eV is reported as a function of the depth of a buried D2O layer in an H2O film. H2 is produced consistently in all measurements, reflecting the H2O component of the film, though it does exhibit a modest reduction in intensity at the time corresponding to product escape from the buried D2O layer. In contrast, HD and D2 production exhibit peaks at times corresponding to product escape from the buried D2O layer in the composite film. These features broaden the deeper the HD or D2 is formed due to diffusion. A simple random-walk model is presented that can qualitatively explain the appearance profile of these peaks as a function of the incident electron penetration.
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Affiliation(s)
- Kamel A K Gadallah
- School of Engineering and Physical Sciences, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, UK and Astronomy & Meteorology Department, Faculty of Science, Al-Azhar University, Nasr City, PO Box 11884, Cairo, Egypt.
| | - Demian Marchione
- School of Engineering and Physical Sciences, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, UK and Science Division, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
| | - Sven P K Koehler
- School of Chemistry, The University of Manchester, Manchester, M13 9PL, UK and Dalton Cumbrian Facility, The University of Manchester, Westlakes Science & Technology Park, Moor Row, CA24 3HA, UK
| | - Martin R S McCoustra
- School of Engineering and Physical Sciences, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, UK
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Taj S, Baird D, Rosu-Finsen A, McCoustra MRS. Surface heterogeneity and inhomogeneous broadening of vibrational line profiles. Phys Chem Chem Phys 2017; 19:7990-7995. [PMID: 28263326 DOI: 10.1039/c6cp07530d] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The surface heterogeneity of amorphous silica (aSiO2) has been probed using coverage dependent temperature programmed desorption (TPD) of a simple probe molecule, carbon monoxide (CO), and is used to explain the inhomogeneous broadening of the CO stretching vibration in the infrared.
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Affiliation(s)
- Skandar Taj
- Institute of Chemical Sciences
- Heriot-Watt University
- Edinburgh
- UK
| | - Diane Baird
- Institute of Chemical Sciences
- Heriot-Watt University
- Edinburgh
- UK
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Marchione D, McCoustra MRS. Non-covalent interaction of benzene with methanol and diethyl ether solid surfaces. Phys Chem Chem Phys 2016; 18:20790-801. [DOI: 10.1039/c6cp01787h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We have investigated the interactions involved at the interface of binary, layered ices (benzene on methanol and on diethyl ether) by means of laboratory experiments and ab initio calculations on model clusters.
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Marchione D, Thrower JD, McCoustra MRS. Efficient electron-promoted desorption of benzene from water ice surfaces. Phys Chem Chem Phys 2016; 18:4026-34. [DOI: 10.1039/c5cp06537b] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We study the desorption of benzene from solid water surfaces during irradiation of ultrathin solid films with low energy electrons.
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Marchione D, McCoustra MRS. Electrons, excitons and hydrogen bonding: electron-promoted desorption from molecular ice surfaces. Phys Chem Chem Phys 2016; 18:29747-29755. [DOI: 10.1039/c6cp05814k] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Desorption of benzene from methanol and diethyl ether ices during irradiation with 250 eV electrons is reported and compared with our previous work on benzene/water ices to highlight the role of hydrogen bonding in excitation transport.
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Rosu-Finsen A, Marchione D, Salter TL, Stubbing JW, Brown WA, McCoustra MRS. Peeling the astronomical onion. Phys Chem Chem Phys 2016; 18:31930-31935. [DOI: 10.1039/c6cp05751a] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
This work presents a study of water mobility on interstellar dust grain analogues at temperatures as low as 18 K. The work indicates that water forms pure domains rather than covering the entire grain, thereby leaving bare dust grain surfaces available on which other molecules can adsorb as well as themselves providing surfaces for further adsorption from the interstellar gas.
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Abdulgalil AGM, Marchione D, Thrower JD, Collings MP, McCoustra MRS, Islam F, Palumbo ME, Congiu E, Dulieu F. Laboratory studies of electron and ion irradiation of solid acetonitrile (CH₃CN). PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2013; 371:20110586. [PMID: 23734051 DOI: 10.1098/rsta.2011.0586] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The structure and bonding of solid acetonitrile (CH₃CN) films on amorphous silica are studied, and chemical and physical processes under irradiation with 200 keV protons and 250-400 eV electrons are quantified using transmission infrared spectroscopy, reflection-absorption infrared spectroscopy and temperature-programmed desorption, with the assistance of basic computational chemistry and nuclear materials calculations. The thermal desorption profiles are found to depend strongly on the balance between CH₃CN-surface and CH₃CN-CH₃CN interactions, passing from a sub-monolayer regime (binding energy: 35-50 kJ mol⁻¹) to a multilayer regime (binding energy: 38.2±1.0 kJ mol⁻¹) via a fractional order desorption regime characteristic of islanding as the coverage increases. Calculations using the SRIM code reveal that the effects of the ion irradiation are dominated by electronic stopping of incident protons, and the subsequent generation of secondary electrons. Therefore, ion irradiation and electron irradiation experiments can be quantitatively compared. During ion irradiation of thicker CH₃CN films, a cross section for secondary electron-promoted chemical destruction of CH3CN of 4 (±1) × 10⁻¹⁸ cm² was measured, while electron-promoted desorption was not detected. A significantly higher cross section for electron-promoted desorption of 0.82-3.2 × 10⁻¹⁵ cm² was measured during electron irradiation of thinner CH₃CN films, while no chemical products were detected. The differences between the experimental results can be rationalized by recognizing that chemical reaction is a bulk effect in the CH₃CN film, whereas desorption is a surface sensitive process. In thicker films, electron-promoted desorption is expected to occur a rate that is independent of the film thickness; i.e. show zeroth-order kinetics with respect to the surface concentration.
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Affiliation(s)
- A G M Abdulgalil
- School of Engineering and Physical Sciences, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, UK
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Thrower J, Collings M, Rutten F, McCoustra M. Highly efficient electron-stimulated desorption of benzene from amorphous solid water ice. Chem Phys Lett 2011. [DOI: 10.1016/j.cplett.2011.02.029] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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17
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Rimola A, Civalleri B, Ugliengo P. Physisorption of aromatic organic contaminants at the surface of hydrophobic/hydrophilic silica geosorbents: a B3LYP-D modeling study. Phys Chem Chem Phys 2010; 12:6357-66. [DOI: 10.1039/c000009d] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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