Atomic ESR relaxation in tritiated solid hydrogen

Collins, G. W.; Maienschein, J L; Mapoles, E. R.; Tsugawa, R.T.; Fearon, E. M.; Souers, P. C.; Gaines, J. R.; Fedders, Peter A.

doi:10.1103/physrevb.48.12620

Cited by 16 publications

(13 citation statements)

References 18 publications

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“…Collins et al [9] also measured a long spin-lattice relaxation time, T 1 = 100 ms, for their sample of solid D 2 with the atomic concentration of ∼10 −4 . Simulating the EPR lines as a mixture of Lorentzian and Gaussian shapes, the authors calculated a fraction of the Lorentzian line component to be rather marked: 0.7 ± 0.3.…”

Section: Saturation and Spin-relaxation Timementioning

confidence: 95%

“…Investigation of impurities in solid molecular hydrogens has attracted continuous attention, which is due to both the manifestation of quantum effects in these systems (e.g., 1.9 0.28 (7) β-Irradiation [1] 1.8 -β-Irradiation [9] 1.5 −0.28 (2) Deposition [12] quantum diffusion of impurity particles, ortho-para conversion of matrix molecules, isotope exchange reactions) and the quest for better cryogenic fuel. Some studies with the use of EPR spectroscopy [1][2][3] provide a circumstantial evidence that a good part of H, D, and T atoms trap at the imperfections of the crystal lattices of solid molecular hydrogens, H 2 , D 2 , T 2 , which may govern the quantum diffusion rate [2] and estimation of the energy stored in the matrix.…”

Section: Introductionmentioning

confidence: 99%

“…Different kinds of irradiation were also employed. Among them: exposition of solid hydrogens to the cobalt-60 source irradiation [7,8], preparation of samples of D atoms matrix isolated in D 2 by freezing a mixture of a large amount of deuterium with a small amount of tritium at a low-temperature surface [1,9], production of H and D atoms in solid HD and D 2 by X-ray radiolysis of solid D 2 − H 2 (2 mol%) mixture [10]. Gordon et al [11] and later Bernard et al [12,13] used a technique of sample preparation that differs considerably from those described above.…”

Section: Introductionmentioning

confidence: 99%

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EPR Study of H and D Atoms in Quench-Condensed Solid D $$_{2}$$ 2

Dmitriev

2015

J Low Temp Phys

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We present an experimental study of H and D atoms trapped in a solid D 2 matrix. The samples were prepared by quench condensing gaseous nD 2 with small (0.15 %) admixture of molecular nH 2 on a substrate at 1.3-4.2 K. An EPR observation revealed two types of H and D atoms: with narrow-and broad-line spectra. In order to elucidate the origin of the centers we performed an analysis that included comparing the matrix shifts of the hyperfine structure constants, considering the saturation and spin-relaxation times, estimation of the superhyperfine broadening, and evaluation of an effect which the tunneling isotope exchange reaction has on the H and D atoms relative EPR intensities. As a result, the broad-line H and D spectra were attributed to atoms at the substitutional positions in the regular D 2 lattice, while the narrow-line spectra were due to atoms trapped at the one-dimensional structure imperfections (like dislocations). These trapped atoms are capable of moving quickly along the defects with a diffusion coefficient D ≈ 4 × 10 −6 cm 2 /s. The results were compared to earlier observations which allowed us to build a suggestion about the nature of previously found atomic centers in D 2 not explained in the literature.

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Section: Saturation and Spin-relaxation Timementioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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EPR Study of H and D Atoms in Quench-Condensed Solid D $$_{2}$$ 2

Dmitriev

2015

J Low Temp Phys

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“…with a 2% T 2 admixture [6], while densities approaching 10 20 cm −3 were reached in pure tritium [7]. The method where β-decay of tritium produces free radicals was pioneered by Lambe [8] who studied radiation induced defects in solid T 2 and by Sharnoff and Pound who studied accumulation and dynamic nuclear polarization of D in solid D 2 [9].…”

Section: Introductionmentioning

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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“…Nevertheless, researchers in the 1950s were never able to obtain concentrations exceeding about 0.01%, far below the criterion for any practical energy storage applications. So far the highest densities of H atoms in bulk (molecular matrices of hydrogen isotopes), 7·10 18 cm -3 , were obtained at T = 1.4 K [9].…”

Section: Introductionmentioning

confidence: 99%