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Brann M, Hansknecht SP, Ma X, Sibener SJ. Differential Condensation of Methane Isotopologues Leading to Isotopic Enrichment under Non-equilibrium Gas-Surface Collision Conditions. J Phys Chem A 2021; 125:9405-9413. [PMID: 34658236 PMCID: PMC8558857 DOI: 10.1021/acs.jpca.1c07826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 10/05/2021] [Indexed: 11/30/2022]
Abstract
We examine the initial differential sticking probability of CH4 and CD4 on CH4 and CD4 ices under nonequilibrium flow conditions using a combination of experimental methods and numerical simulations. The experimental methods include time-resolved in situ reflection-absorption infrared spectroscopy (RAIRS) for monitoring on-surface gaseous condensation and complementary King and Wells mass spectrometry techniques for monitoring sticking probabilities that provide confirmatory results via a second independent measurement method. Seeded supersonic beams are employed so that the entrained CH4 and CD4 have the same incident velocity but different kinetic energies and momenta. We found that as the incident velocity of CH4 and CD4 increases, the sticking probabilities for both molecules on a CH4 condensed film decrease systematically, but that preferential sticking and condensation occur for CD4. These observations differ when condensed CD4 is used as the target interface, indicating that the film's phonon and rovibrational densities of states, and collisional energy transfer cross sections, have a role in differential energy accommodation between isotopically substituted incident species. Lastly, we employed a mixed incident supersonic beam composed of both CH4 and CD4 in a 3:1 ratio and measured the condensate composition as well as the sticking probability. When doing so, we see the same effect in the condensed mixed film, supporting an isotopic enrichment of the heavier isotope. We propose that enhanced multi-phonon interactions and inelastic cross sections between the incident CD4 projectile and the CH4 film allow for more efficacious gas-surface energy transfer. VENUS code MD simulations show the same sticking probability differences between isotopologues as observed in the gas-surface scattering experiments. Ongoing analyses of these trajectories will provide additional insights into energy and momentum transfer between the incident species and the interface. These results offer a new route for isotope enrichment via preferential condensation of heavier isotopes and isotopologues during gas-surface collisions under specifically selected substrate, gas-mixture, and incident velocity conditions. They also yield valuable insights into gaseous condensation under non-equilibrium conditions such as occur in aircraft flight in low-temperature environments. Moreover, these results can help to explain the increased abundance of deuterium in solar system planets and can be incorporated into astrophysical models of interstellar icy dust grain surface processes.
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Affiliation(s)
- Michelle
R. Brann
- The James Franck Institute
and Department of Chemistry, The University
of Chicago, 929 E. 57th Street, Chicago, Illinois 60637, United
States
| | - Stephen P. Hansknecht
- The James Franck Institute
and Department of Chemistry, The University
of Chicago, 929 E. 57th Street, Chicago, Illinois 60637, United
States
| | - Xinyou Ma
- The James Franck Institute
and Department of Chemistry, The University
of Chicago, 929 E. 57th Street, Chicago, Illinois 60637, United
States
| | - S. J. Sibener
- The James Franck Institute
and Department of Chemistry, The University
of Chicago, 929 E. 57th Street, Chicago, Illinois 60637, United
States
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Bhandari A, Rollings AP, Ratto L, Weinstein JD. High-purity solid parahydrogen. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:073202. [PMID: 34340409 DOI: 10.1063/5.0049006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Accepted: 06/11/2021] [Indexed: 06/13/2023]
Abstract
Alkali atoms trapped in solid hydrogen matrices have demonstrated ultralong electron spin coherence times and are promising as quantum sensors. Their spin coherence is limited by magnetic noise from naturally occurring orthohydrogen molecules in the parahydrogen matrix. In the gas phase, the orthohydrogen component of hydrogen can be converted to parahydrogen by flowing it over a catalyst held at cryogenic temperatures, with lower temperatures giving a lower orthohydrogen fraction. In this work, we use a single cryostat to reduce the orthohydrogen fraction of hydrogen gas and grow a solid matrix from the resulting high-purity parahydrogen. We demonstrate the operation of the catalyst down to a temperature of 8 K, and we spectroscopically verify that orthohydrogen impurities in the resulting solid are at a level <10-6. We also find that, at sufficiently low temperatures, the cryogenic catalyst provides isotopic purification, reducing the HD fraction.
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Affiliation(s)
- Ashok Bhandari
- Department of Physics, University of Nevada, Reno, Nevada 89557, USA
| | | | - Levi Ratto
- Department of Physics, University of Nevada, Reno, Nevada 89557, USA
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Molpeceres G, Kästner J. Adsorption of H 2 on amorphous solid water studied with molecular dynamics simulations. Phys Chem Chem Phys 2020; 22:7552-7563. [PMID: 32222747 DOI: 10.1039/d0cp00250j] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
We investigated the behavior of H2, the main constituent of the gas phase in dense clouds, after collision with amorphous solid water (ASW) surfaces, one of the most abundant chemical species of interstellar ices. We developed a general framework to study the adsorption dynamics of light species on interstellar ices. We provide binding energies and their distribution, sticking probabilities for incident energies between 1 meV and 60 meV, and thermal sticking coefficients between 10 and 300 K for surface temperatures from 10 to 110 K. We found that the sticking probability depends strongly on the adsorbate kinetic energy and the surface temperature, but hardly on the angle of incidence. We observed finite sticking probabilities above the thermal desorption temperature. Adsorption and thermal desorption should be considered as separate events with separate time scales. Laboratory results for these species have shown a gap in the trends attributed to the differently utilized experimental techniques. Our results complement observations and extend them, increasing the range of gas temperatures under consideration. We plan to use our method to study a variety of adsorbates, including radicals and charged species.
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Affiliation(s)
- Germán Molpeceres
- Institute for Theoretical Chemistry, University of Stuttgart, 70569 Stuttgart, Germany.
| | - Johannes Kästner
- Institute for Theoretical Chemistry, University of Stuttgart, 70569 Stuttgart, Germany.
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4
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Wakelam V, Bron E, Cazaux S, Dulieu F, Gry C, Guillard P, Habart E, Hornekær L, Morisset S, Nyman G, Pirronello V, Price SD, Valdivia V, Vidali G, Watanabe N. H 2 formation on interstellar dust grains: The viewpoints of theory, experiments, models and observations. ACTA ACUST UNITED AC 2017. [DOI: 10.1016/j.molap.2017.11.001] [Citation(s) in RCA: 90] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Mella M, Curotto E. Quest for Inexpensive Hydrogen Isotopic Fractionation: Do We Need 2D Quantum Confining in Porous Materials or Are Rough Surfaces Enough? The Case of Ammonia Nanoclusters. J Phys Chem A 2016; 120:8148-8159. [PMID: 27704841 DOI: 10.1021/acs.jpca.6b08005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We study the adsorption energetics and quantum properties of the molecular hydrogen isotopes H2, D2, and T2 onto the surface of rigid ammonia nanoclusters with quantum simulations and accurate model potential energy surfaces (PES). A highly efficient diffusion Monte Carlo (DMC) algorithm for rigid rotors allowed us to accurately define zero-point adsorption energies for the three isotopes, as well as the degree of translational and rotational delocalization that each affords on the surface. From the data emerges that the quantum adsorption energy (Eads) of T2 can be up to twice the one of H2 at 0 K, suggesting the possibility of exploiting some form of solid ammonia to selectivity separate hydrogen isotopes at low temperatures (≃20 K). This is discussed by focusing on the structural motif that may be more effective for the task. The analysis of the contributions to Eads, however, surprisingly indicates that the average kinetic energy (Ekin) and rotation energy (Erotkin) of T2 can also be, respectively, 2 times and 20 times higher than those of H2; this finding markedly deviates from what is predicted for hydrogen molecules inside carbon nanotubes (CNT) or metallic-organic frameworks (MOF), where Ekin and Erotkin is higher for H2 due to the unavoidable effects of confinement and hindrance to its rotational motion. The rationale for these differences is provided by the geometrical distributions for the rigid rotors, which reveal an increasingly stronger coupling between rotational and translational degrees of freedom upon increasing the isotopic mass. This effect has never been observed before on adsorbing surfaces (e.g., graphite) and is induced by a strongly anisotropic and anharmonic bowl-like potential experienced by the rotors.
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Affiliation(s)
- Massimo Mella
- Dipartimento di Scienza ed Alta Tecnologia, Università degli Studi dell'Insubria , via Valleggio 9, 22100 Como, Italy
| | - E Curotto
- Department of Chemistry and Physics, Arcadia University , Glenside, Pennsylvania 19038-3295, United States
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Raut U, Mitchell EH, Baragiola RA. ION IRRADIATION OF H2-LADEN POROUS WATER-ICE FILMS: IMPLICATIONS FOR INTERSTELLAR ICES. ACTA ACUST UNITED AC 2015. [DOI: 10.1088/0004-637x/811/2/120] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Amiaud L, Fillion JH, Dulieu F, Momeni A, Lemaire JL. Physisorption and desorption of H2, HD and D2 on amorphous solid water ice. Effect on mixing isotopologue on statistical population of adsorption sites. Phys Chem Chem Phys 2015; 17:30148-57. [DOI: 10.1039/c5cp03985a] [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
We study the adsorption and desorption of three isotopologues of molecular hydrogen mixed on 10 ML of porous amorphous water ice (ASW) deposited at 10 K.
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Affiliation(s)
- Lionel Amiaud
- Institut des Sciences Moléculaires d'Orsay (ISMO)
- CNRS
- University Paris-Sud
- Université Paris-Saclay
- F-91405 Orsay
| | | | - François Dulieu
- LERMA
- Observatoire de Paris
- PSL Research University
- CNRS
- Sorbonnes Universités
| | - Anouchah Momeni
- Institut des Sciences Moléculaires d'Orsay (ISMO)
- CNRS
- University Paris-Sud
- Université Paris-Saclay
- F-91405 Orsay
| | - Jean-Louis Lemaire
- Institut des Sciences Moléculaires d'Orsay (ISMO)
- CNRS
- University Paris-Sud
- Université Paris-Saclay
- F-91405 Orsay
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Walsh C, Herbst E, Nomura H, Millar TJ, Weaver SW. Complex organic molecules along the accretion flow in isolated and externally irradiated protoplanetary disks. Faraday Discuss 2014; 168:389-421. [DOI: 10.1039/c3fd00135k] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The birth environment of the Sun will have influenced the physical and chemical structure of the pre-solar nebula, including the attainable chemical complexity reached in the disk, important for prebiotic chemistry. The formation and distribution of complex organic molecules (COMs) in a disk around a T Tauri star is investigated for two scenarios: (i) an isolated disk, and (ii) a disk irradiated externally by a nearby massive star. The chemistry is calculated along the accretion flow from the outer disk inwards using a comprehensive network which includes gas-phase reactions, gas-grain interactions, and thermal grain-surface chemistry. Two simulations are performed, one beginning with complex ices and one with simple ices only. For the isolated disk, COMs are transported without major chemical alteration into the inner disk where they thermally desorb into the gas reaching an abundance representative of the initial assumed ice abundance. For simple ices, COMs can efficiently form on grain surfaces under the conditions in the outer disk. Gas-phase COMs are released into the molecular layer via photodesorption. For the irradiated disk, complex ices are also transported inwards; however, they undergo thermal processing caused by the warmer conditions in the irradiated disk which tends to reduce their abundance along the accretion flow. For simple ices, grain-surface chemistry cannot efficiently synthesise COMs in the outer disk because the necessary grain-surface radicals, which tend to be particularly volatile, are not sufficiently abundant on the grain surfaces. Gas-phase COMs are formed in the inner region of the irradiated disk via gas-phase chemistry induced by the desorption of strongly bound molecules such as methanol; hence, the abundances are not representative of the initial molecular abundances injected into the outer disk. These results suggest that the composition of comets formed in isolated disks may differ from those formed in externally irradiated disks with the latter composed of more simple ices.
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Affiliation(s)
- Catherine Walsh
- Leiden Observatory
- Leiden University
- 2300 RA Leiden, The Netherlands
| | - Eric Herbst
- Departments of Chemistry, Astronomy, and Physics, University of Virginia
- Charlottesville, USA
| | - Hideko Nomura
- Department of Earth and Planetary Sciences
- Tokyo Institute of Technology
- , Japan
| | - T. J. Millar
- Astrophysics Research Centre
- School of Mathematics and Physics
- Queen's University Belfast
- Belfast, UK
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van Dishoeck EF. Astrochemistry of dust, ice and gas: introduction and overview. Faraday Discuss 2014; 168:9-47. [DOI: 10.1039/c4fd00140k] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A brief introduction and overview of the astrochemistry of dust, ice and gas and their interplay is presented. The importance of basic chemical physics studies of critical reactions is illustrated through a number of recent examples. Such studies have also triggered new insight into chemistry, illustrating how astronomy and chemistry can enhance each other. Much of the chemistry in star- and planet-forming regions is now thought to be driven by gas–grain chemistry rather than pure gas-phase chemistry, and a critical discussion of the state of such models is given. Recent developments in studies of diffuse clouds and PDRs, cold dense clouds, hot cores, protoplanetary disks and exoplanetary atmospheres are summarized, both for simple and more complex molecules, with links to papers presented in this volume. In spite of many lingering uncertainties, the future of astrochemistry is bright: new observational facilities promise major advances in our understanding of the journey of gas, ice and dust from clouds to planets.
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Affiliation(s)
- Ewine F. van Dishoeck
- Leiden Observatory
- Leiden University
- 2300 RA Leiden, the Netherlands
- Max-Planck-Institute für Extraterrestrische Physik
- Garching, Germany
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10
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Affiliation(s)
- Gianfranco Vidali
- Syracuse University , 201 Physics Building, Syracuse, New York 13244, United States
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Hama T, Watanabe N. Surface Processes on Interstellar Amorphous Solid Water: Adsorption, Diffusion, Tunneling Reactions, and Nuclear-Spin Conversion. Chem Rev 2013; 113:8783-839. [DOI: 10.1021/cr4000978] [Citation(s) in RCA: 211] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tetsuya Hama
- Institute of Low Temperature
Science, Hokkaido University, N19W8 Kita-ku, Sapporo, Hokkaido 060-0819, Japan
| | - Naoki Watanabe
- Institute of Low Temperature
Science, Hokkaido University, N19W8 Kita-ku, Sapporo, Hokkaido 060-0819, Japan
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Congiu E, Chaabouni H, Laffon C, Parent P, Baouche S, Dulieu F. Efficient surface formation route of interstellar hydroxylamine through NO hydrogenation. I. The submonolayer regime on interstellar relevant substrates. J Chem Phys 2012; 137:054713. [DOI: 10.1063/1.4738895] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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