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Ueta H, Fukutani K, Yamakawa K. Fast ortho-to-para conversion of molecular hydrogen in chemisorption and matrix-isolation systems. Front Chem 2023; 11:1258035. [PMID: 37711317 PMCID: PMC10497966 DOI: 10.3389/fchem.2023.1258035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Accepted: 07/27/2023] [Indexed: 09/16/2023] Open
Abstract
Molecular hydrogen has two nuclear-spin modifications called ortho and para. Because of the symmetry restriction with respect to permutation of the two protons, the ortho and para isomers take only odd and even values of the rotational quantum number, respectively. The ortho-to-para conversion is promoted in condensed systems, to which the excess rotational energy and spin angular momentum are transferred. We review recent studies on fast ortho-to-para conversion of hydrogen in molecular chemisorption and matrix isolation systems, discussing the conversion mechanism as well as rotational-relaxation pathways.
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Affiliation(s)
- Hirokazu Ueta
- Advanced Science Research Center, Japan Atomic Energy Agency, Ibaraki, Japan
| | - Katsuyuki Fukutani
- Advanced Science Research Center, Japan Atomic Energy Agency, Ibaraki, Japan
- Institute of Industrial Science, The University of Tokyo, Tokyo, Japan
| | - Koichiro Yamakawa
- Advanced Science Research Center, Japan Atomic Energy Agency, Ibaraki, Japan
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2
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Emtiaz SM, Toriello F, He J, Vidali G. Infrared Spectroscopic Study of Methane Ice, Pure and in Mixtures with Polar (H 2O) and Nonpolar (N 2) Molecules. J Phys Chem A 2022; 126:1973-1979. [PMID: 35302374 PMCID: PMC8978181 DOI: 10.1021/acs.jpca.2c00287] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mid-infrared studies of fundamental modes of ices of pure CH4 and its mixtures with polar (H2O) and nonpolar (e.g., N2) molecules are essential in order to learn the state of aggregation and thermal history of ices present in the interstellar medium and outer solar system bodies. Such data will be useful in the interpretation of observational data from the James Webb Space Telescope. Using an ultrahigh vacuum apparatus, we conducted reflection-absorption infrared spectroscopy measurements in the mid-IR range of pure methane ice and methane-containing ice mixtures of interest to interstellar and solar system ice chemistry, e.g., with H2O and N2 molecules. We found that nuclear spin conversion (NSC) in solid methane and its crystalline structures is affected─in different ways─by the presence of H2O and N2. Specifically, we found a relationship between the thickness and the solid-state ordering transformation in methane thin films. This new study of the NSC of pure CH4 ice and of the CH4:H2O ice mixture at 7 K is carried out in relation to the segregation of H2O using the ν1 and ν2 IR inactive modes of methane. The diffusion of N2 and CH4 in the CH4:N2 ice mixture with temperature cycling has been studied to obtain the relationship between IR features and the state of aggregation of the ice.
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Affiliation(s)
- Shahnewaz M Emtiaz
- Physics Department, Syracuse University, Syracuse, New York 13244, United States
| | - Francis Toriello
- Physics Department, Syracuse University, Syracuse, New York 13244, United States
| | - Jiao He
- Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany
| | - Gianfranco Vidali
- Physics Department, Syracuse University, Syracuse, New York 13244, United States
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3
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Sugimoto T, Yamakawa K. Nuclear-spin conversion analysis of ν 2 + ν 4 combination band of crystalline methane in phase II. J Chem Phys 2021; 154:026101. [PMID: 33445921 DOI: 10.1063/5.0031272] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We conducted reflection-absorption infrared spectroscopy in an ultrahigh vacuum and observed the ν2 + ν4 combination band of crystalline methane in phase II, where the rotating and librating species coexist. We analyzed the time- and temperature-dependence of the spectrum due to the nuclear-spin conversion of methane to update the assignment of the rotational and librational structure of this band. The conversion analysis performed in the present work will also be applicable to the detailed assignments of overtones and other combination bands.
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Affiliation(s)
- Takeru Sugimoto
- Department of Physics, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo 171-8588, Japan
| | - Koichiro Yamakawa
- Advanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai, Naka, Ibaraki 319-1195, Japan
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Emtiaz SM, Toriello F, He J, Vidali G. Infrared Spectroscopic Study of Solid Methane: Nuclear Spin Conversion of Stable and Metastable Phases. J Phys Chem A 2020; 124:552-559. [PMID: 31891499 DOI: 10.1021/acs.jpca.9b10643] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Infrared spectroscopy was employed to study thin films of solid methane at low temperatures. We report new measurements of temporal changes of infrared spectra of methane ice in the ν3 and ν4 bands due to nuclear spin conversion upon rapid cooling from 30 to 6.0-11.0 K. The relaxation rates of the nuclear spin were found to be a function of temperature. The activation energy associated with the relaxation has been determined over an extended temperature range. We also found a new metastable phase of methane ice upon deposition at T < 7 K. After the deposition at 6 K and annealed to a higher temperature, a phase transition from the metastable phase to a stable crystalline phase takes place. We found that the relaxation has different activation energies below and above 8.5 K. From a quantitative analysis of the ν3 and ν4 IR bands, we suggest that the metastable phase is a crystalline phase with a degree of orientational disorder between the two known stable solid phases.
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Affiliation(s)
- Shahnewaz M Emtiaz
- Physics Department , Syracuse University , Syracuse , New York 13244 , United States
| | - Francis Toriello
- Physics Department , Syracuse University , Syracuse , New York 13244 , United States
| | - Jiao He
- Laboratory for Astrophysics, Leiden Observatory , Leiden University , 2300 RA Leiden , Netherlands
| | - Gianfranco Vidali
- Physics Department , Syracuse University , Syracuse , New York 13244 , United States
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Peterson KI, Pullman DP, Lin W, Minei AJ, Arsenault EA, Novick SE. Structure and Dynamics of the Methane-Propane van der Waals Complex. J Phys Chem A 2019; 123:5274-5282. [DOI: 10.1021/acs.jpca.9b02486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Karen I. Peterson
- Department of Chemistry and Biochemistry, San Diego State University, 5500 Campanile Road, San Diego, California 92182-1030, United States
| | - D. P. Pullman
- Department of Chemistry and Biochemistry, San Diego State University, 5500 Campanile Road, San Diego, California 92182-1030, United States
| | - Wei Lin
- Department of Chemistry, University of Texas Rio Grande Valley, Brownsville, Texas, United States
| | - Andrea J. Minei
- Department of Chemistry and Biochemistry, Division of Natural Sciences, College of Mount Saint Vincent, 6301 Riverdale Avenue, Riverdale, New York 10471, United States
| | - Eric A. Arsenault
- Department of Chemistry, Wesleyan University, 52 Lawn Avenue, Middletown, Connecticut 06459, United States
| | - Stewart E. Novick
- Department of Chemistry, Wesleyan University, 52 Lawn Avenue, Middletown, Connecticut 06459, United States
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Sugimoto T, Nasu H, Arakawa I, Yamakawa K. Spectroscopic determination of interconversion rates among three nuclear spin isomers of methane in crystalline II. J Chem Phys 2019; 150:184302. [PMID: 31091910 DOI: 10.1063/1.5091070] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We measured infrared absorption spectra of crystalline II of CH4 and succeeded in detecting a prominent Q(2) peak in the ν3 vibrational region by rapid cooling after annealing as well as previously reported rovibrational and librational-vibrational peaks. The integral intensities of the R(0), R(1), and Q(2) peaks were found to show biexponential dependence on time. This clearly demonstrates the interconversion among the three nuclear-spin isomers occupying low-lying rotational levels. The two relaxation rates obtained by biexponential fitting were (0.48, 2.3), (1.1, 4.1), (2.3, 5.1), and (3.4, 15.3) in units of inverse hour (h-1) at 5.2, 6.0, 6.5, and 7.0 K, respectively.
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Affiliation(s)
- Takeru Sugimoto
- Department of Physics, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo 171-8588, Japan
| | - Hirokazu Nasu
- Department of Physics, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo 171-8588, Japan
| | - Ichiro Arakawa
- Department of Physics, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo 171-8588, Japan
| | - Koichiro Yamakawa
- Department of Physics, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo 171-8588, Japan
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Bloodworth S, Sitinova G, Alom S, Vidal S, Bacanu GR, Elliott SJ, Light ME, Herniman JM, Langley GJ, Levitt MH, Whitby RJ. First Synthesis and Characterization of CH 4 @C 60. Angew Chem Int Ed Engl 2019; 58:5038-5043. [PMID: 30773760 PMCID: PMC6492075 DOI: 10.1002/anie.201900983] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Indexed: 11/30/2022]
Abstract
The endohedral fullerene CH4 @C60 , in which each C60 fullerene cage encapsulates a single methane molecule, has been synthesized for the first time. Methane is the first organic molecule, as well as the largest, to have been encapsulated in C60 to date. The key orifice contraction step, a photochemical desulfinylation of an open fullerene, was completed, even though it is inhibited by the endohedral molecule. The crystal structure of the nickel(II) octaethylporphyrin/ benzene solvate shows no significant distortion of the carbon cage, relative to the C60 analogue, and shows the methane hydrogens as a shell of electron density around the central carbon, indicative of the quantum nature of the methane. The 1 H spin-lattice relaxation times (T1 ) for endohedral methane are similar to those observed in the gas phase, indicating that methane is freely rotating inside the C60 cage. The synthesis of CH4 @C60 opens a route to endofullerenes incorporating large guest molecules and atoms.
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Affiliation(s)
- Sally Bloodworth
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of SouthamptonSouthamptonSO17 1BJUK
| | - Gabriela Sitinova
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of SouthamptonSouthamptonSO17 1BJUK
| | - Shamim Alom
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of SouthamptonSouthamptonSO17 1BJUK
| | - Sara Vidal
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of SouthamptonSouthamptonSO17 1BJUK
| | - George R. Bacanu
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of SouthamptonSouthamptonSO17 1BJUK
| | - Stuart J. Elliott
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of SouthamptonSouthamptonSO17 1BJUK
- Current address: Centre de Résonance Magnétique Nucléaire à Très Hauts ChampsFRE 2034 Université de LyonCNRSUniversité Claude Bernard Lyon 1ENS de Lyon5 Rue de la Doua69100VilleurbanneFrance
| | - Mark E. Light
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of SouthamptonSouthamptonSO17 1BJUK
| | - Julie M. Herniman
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of SouthamptonSouthamptonSO17 1BJUK
| | - G. John Langley
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of SouthamptonSouthamptonSO17 1BJUK
| | - Malcolm H. Levitt
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of SouthamptonSouthamptonSO17 1BJUK
| | - Richard J. Whitby
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of SouthamptonSouthamptonSO17 1BJUK
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Bloodworth S, Sitinova G, Alom S, Vidal S, Bacanu GR, Elliott SJ, Light ME, Herniman JM, Langley GJ, Levitt MH, Whitby RJ. First Synthesis and Characterization of CH
4
@C
60. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201900983] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Sally Bloodworth
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of Southampton Southampton SO17 1BJ UK
| | - Gabriela Sitinova
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of Southampton Southampton SO17 1BJ UK
| | - Shamim Alom
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of Southampton Southampton SO17 1BJ UK
| | - Sara Vidal
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of Southampton Southampton SO17 1BJ UK
| | - George R. Bacanu
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of Southampton Southampton SO17 1BJ UK
| | - Stuart J. Elliott
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of Southampton Southampton SO17 1BJ UK
- Current address: Centre de Résonance Magnétique Nucléaire à Très Hauts ChampsFRE 2034 Université de LyonCNRSUniversité Claude Bernard Lyon 1ENS de Lyon 5 Rue de la Doua 69100 Villeurbanne France
| | - Mark E. Light
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of Southampton Southampton SO17 1BJ UK
| | - Julie M. Herniman
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of Southampton Southampton SO17 1BJ UK
| | - G. John Langley
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of Southampton Southampton SO17 1BJ UK
| | - Malcolm H. Levitt
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of Southampton Southampton SO17 1BJ UK
| | - Richard J. Whitby
- Chemistry, Faculty of Engineering and Physical SciencesUniversity of Southampton Southampton SO17 1BJ UK
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Ueta H, Watanabe N, Hama T, Kouchi A. Surface Temperature Dependence of Hydrogen Ortho-Para Conversion on Amorphous Solid Water. PHYSICAL REVIEW LETTERS 2016; 116:253201. [PMID: 27391719 DOI: 10.1103/physrevlett.116.253201] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Indexed: 06/06/2023]
Abstract
The surface temperature dependence of the ortho-to-para conversion of H_{2} on amorphous solid water is first reported. A combination of photostimulated desorption and resonance-enhanced multiphoton ionization techniques allowed us to sensitively probe the conversion on the surface of amorphous solid water at temperatures of 9.2-16 K. Within a narrow temperature window of 8 K, the conversion time steeply varied from ∼4.1×10^{3} to ∼6.4×10^{2} s. The observed temperature dependence is discussed in the context of previously suggested models and the energy dissipation process. The two-phonon process most likely dominates the conversion rate at low temperatures.
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Affiliation(s)
- Hirokazu Ueta
- Institute of Low Temperature Science (ILTS), Hokkaido University, Sapporo 060-0819, Japan
| | - Naoki Watanabe
- Institute of Low Temperature Science (ILTS), Hokkaido University, Sapporo 060-0819, Japan
| | - Tetsuya Hama
- Institute of Low Temperature Science (ILTS), Hokkaido University, Sapporo 060-0819, Japan
| | - Akira Kouchi
- Institute of Low Temperature Science (ILTS), Hokkaido University, Sapporo 060-0819, Japan
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