Experimental determination of the mechanism of the tunneling diffusion of H atoms in solid hydrogen: Physical exchange versus chemical reaction

Kumada, Takayuki

doi:10.1103/physrevb.68.052301

Cited by 45 publications

(33 citation statements)

References 18 publications

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“…We previously studied the effect of pressure on reaction ͑1͒ in solid HD and H + H 2 → H 2 + H in solid H 2 up to 13 MPa, where a decreases by 1.5%-2%. 23 The rate constants for these reactions at 13 MPa were found to be larger than those at 0 MPa by 6 ± 6%. On the other hand, as long as this model is applicable, E zero at 13 MPa is calculated to be larger than that at 0 MPa by as much as 10%.…”

Section: Discussionmentioning

confidence: 88%

“…This picture is contrasted to that of isothermal reaction H +H 2 → H 2 + H where both of the reactant H + H 2 and products H 2 + H are trapped in the bound states of solid H 2 . 23,24 Rate constant for these dissociation reactions should be the product of collision frequency between neighboring D atoms and H 2 ͑HD͒ molecules and barrier penetration factor P͑E͒ via quantum tunneling. The collision frequency should be their zero-point oscillation frequency ϳE zero / h in solid hydrogens ͑h: Planck's constant͒.…”

Section: Discussionmentioning

confidence: 99%

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Tunneling chemical reactions D+H2→DH+H and D+DH→D2+H in solid D2–H2 and HD–H2 mixtures: An electron-spin-resonance study

Kumada

2006

The Journal of Chemical Physics

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Tunneling chemical reactions D + H2 --> DH + H and D + DH --> D2 + H in solid HD-H2 and D2-H2 mixtures were studied in the temperature range between 4 and 8 K. These reactions were initiated by UV photolysis of DI molecules doped in these solids for 30 s and followed by measuring the time course of electron-spin-resonance (ESR) intensities of D and H atoms. ESR intensity of D atoms produced by the photolysis decreases but that of H atoms increases with time. Time course of the D and H intensities has the fast and slow processes. The fast process, which finishes within approximately 300 s after the photolysis, is assigned to the reaction of D atom with one of its nearest-neighboring H2 molecules, D(H2)n(HD)(12-n) --> H(H2)(n-1)(HD)(13-n) or D(H2)n(D2)(12-n) --> H(HD)(H2)(n-1)(D2)(12-n) for 12 > or = n > or = 1. Rate constant for the D + H2 reaction between neighboring D atom-H2 molecule pair is determined to be (7.5 +/- 0.7) x 10(-3) s(-1) in solid HD-H2 and (1.3+/-0.3) x 10(-2) s(-1) in D2-H2 at 4.1 K, which is very close to that calculated based on the theory of chemical reaction in gas phase by Hancock et al. [J. Chem. Phys. 91, 3492 (1989)] and Takayanagi and Sato [J. Chem. Phys. 92, 2862 (1990)]. This rate constant was found to be independent of temperature up to 7 K within experimental error of +/-30%. The slow process is assigned to the reaction of D atom produced in a cage fully surrounded by HD or D2 molecules, D(HD)12 or D(D2)12. This D atom undergoes the D + DH reaction with one of its nearest-neighboring HD molecules in solid HD-H2 or diffuses to the neighbor of H2 molecules to allow the D + H2 reaction in solid HD-H2 and D2-H2. The former is the main channel in solid HD-H2 below 6 K where D atoms diffuse very slowly, whereas the latter dominates over the former above 6 K. Rate for the reactions in the slow process is independent of temperature below 6 K but increases with the increase in temperature above 6 K. We found that the increase is due to the increase in hopping rate of D atoms to the neighbor of H2 molecules. Rate constant for the D + DH reaction was found to be independent of temperature up to 7 K as well.

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Section: Discussionmentioning

confidence: 88%

Section: Discussionmentioning

confidence: 99%

Tunneling chemical reactions D+H2→DH+H and D+DH→D2+H in solid D2–H2 and HD–H2 mixtures: An electron-spin-resonance study

Kumada

2006

The Journal of Chemical Physics

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“…Recombination of atomic hydrogen in solid hydrogen matrices at low temperatures proceeds in two steps: a diffusion stage when atoms approach each other by the distance of a lattice constant followed by rapid recombination into molecules. Kumada [30] showed that diffusion of hydrogen atoms at temperatures Figure 10. ENDORs of H atoms in matrices of hydrogen isotopes.…”

Section: Discussionmentioning

confidence: 99%

ESR study of atomic hydrogen and tritium in solid T₂and T₂:H₂matrices below 1 K

Sheludiakov

Ahokas

Järvinen

et al. 2017

Phys. Chem. Chem. Phys.

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We report on the first ESR study of atomic hydrogen and tritium stabilized in a solid T2 and T2:H2 matrices down to 70 mK. The concentrations of T atoms in pure T2 approached 2 × 10 20 cm −3 and record-high concentrations of H atoms ∼ 1×10 20 cm −3 were reached in T2: H2 solid mixtures where a fraction of T atoms became converted into H due to the isotopic exchange reaction T+H2 →TH+H.The maximum concentrations of unpaired T and H atoms was limited by their recombination which becomes enforced by efficient atomic diffusion due to a presence of a large number of vacancies and phonons generated in the matrices by β-particles. Recombination also appeared in an explosive manner both being stimulated and spontaneously in thick films where sample cooling was insufficient. We suggest that the main mechanism for H and T migration is physical diffusion related to tunneling or hopping to vacant sites in contrast to isotopic chemical reactions which govern diffusion of H and D atoms created in H2 and D2 matrices by other methods.

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“…The motion of atomic hydrogen in molecular hydrogen has been widely studied [235]. Both thermally activated and quantum tunneling contribute to defect motion, but quantum tunneling dominates at these low temperatures (the two dominant tunneling pathways have energy barriers of 4600K and 100K).…”

Section: General Introduction: Physics Of Atomic Hydrogen Embedded Inmentioning

confidence: 99%

“…Kumada [235] argues on the basis of experimental data that the exchange reaction H + H 2 → H 2 + H is the dominant diffusion mechanism at low temperatures.…”

Section: General Introduction: Physics Of Atomic Hydrogen Embedded Inmentioning

confidence: 99%

Quantum Phase Transitions in Cold Atoms and Low Temperature Solids

Hazzard¹

2011

Springer Theses

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This thesis describes how to create and probe novel phases of matter and exotic (non-quasiparticle) behavior in cold atomic gases. It focuses on situations whose physics is relevant to condensed matter systems, and where open questions about these latter systems can be addressed. It also attempts to better understand several experimental anomalies in condensed matter systems.The thesis is divided into five parts. The first section or chapter of each part gives an introduction to the motivation and background for the physics of that part; the last section or chapter gives an outlook for future studies. Parts 1-4 (Chapters 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15) introduce and show different facets of how to learn about novel physics relevant to condensed matter using cold atomic systems. Part 5 ( Chapters 16, 17, 18, and 19) constrains explanations of several ill-understood phenomena occurring in low-temperature quantum solids and condensed matter systems and attempts to construct mechanisms for their behavior.Part 1 (Chapters 1 and 2) generally motivates and introduces condensed matter, cold atoms, and many-body physics. Part 2 (Chapters 3, 4, 5, 6, and 7) introduces optical lattice physics and describes ways of spectroscopically probing many-body physics, especially dynamics, near quantum phase transitions in these systems. Part 3 (Chapters 8, 9, 10, 11, and 12) discusses the effects of rotation and how this can create exotic states, as well as alternative methods of creating exotic states. This leads us to study optical lattices where particles possess non-trivial correlations between particles even within a site in Chapters 10 and 11. Part 4 (Chapters 13, 14, and 15) introduces another route to studying exotic physics in cold atoms: examining finite temperature behavior near second order quantum phase transitions. In the "quantum critical regime" occurring near these transitions, non-quasiparticle behavior generically manifests. This behavior has been hidden in previous analyses of data, but Chapter 14 introduces a set of tools required to extract universal quantum critical behavior from standard observables in cold atoms experiments. Chapter 15 discusses near-term opportunities to use these tools to impact fundamental, open questions in condensed matter physics.Part 5 (Chapters 16, 17, 18, and 19) introduces several anomalous or interesting experimental results from low-temperature and solid state physics, constrains possible explanations, and attempts to construct mechanisms for their behavior.Chapter 17 shows that collisional properties between quasi-two-dimensional spinpolarized hydrogen atoms are dramatically modified by the presence of a helium film, on which they are invariably adsorbed in present experiments. Chapter 18 constrains theories regarding recent observations on atomic hydrogen defects in molecular hydrogen quantum solids. Finally, Chapter 19 proposes a mechanism for supersolidity that could account for the experimental observations at that time.Since then, it probably has been...

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Experimental determination of the mechanism of the tunneling diffusion of H atoms in solid hydrogen: Physical exchange versus chemical reaction

Cited by 45 publications

References 18 publications

Tunneling chemical reactions D+H2→DH+H and D+DH→D2+H in solid D2–H2 and HD–H2 mixtures: An electron-spin-resonance study

Tunneling chemical reactions D+H2→DH+H and D+DH→D2+H in solid D2–H2 and HD–H2 mixtures: An electron-spin-resonance study

ESR study of atomic hydrogen and tritium in solid T₂and T₂:H₂matrices below 1 K

Quantum Phase Transitions in Cold Atoms and Low Temperature Solids

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Experimental determination of the mechanism of the tunneling diffusion of H atoms in solid hydrogen: Physical exchange versus chemical reaction

Cited by 45 publications

References 18 publications

Tunneling chemical reactions D+H2→DH+H and D+DH→D2+H in solid D2–H2 and HD–H2 mixtures: An electron-spin-resonance study

Tunneling chemical reactions D+H2→DH+H and D+DH→D2+H in solid D2–H2 and HD–H2 mixtures: An electron-spin-resonance study

ESR study of atomic hydrogen and tritium in solid T2and T2:H2matrices below 1 K

Quantum Phase Transitions in Cold Atoms and Low Temperature Solids

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Product

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ESR study of atomic hydrogen and tritium in solid T₂and T₂:H₂matrices below 1 K