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  1. Article ; Online: Purely Spatial Quantum Diffusion of H Atoms in Solid H_{2} at Temperatures below 1 K.

    Sheludiakov, S / Lee, D M / Khmelenko, V V / Järvinen, J / Ahokas, J / Vasiliev, S

    Physical review letters

    2021  Volume 126, Issue 19, Page(s) 195301

    Abstract: We report on a direct measurement of the quantum diffusion of H atoms in solid molecular hydrogen films at T=0.7  K. We obtained a rate of pure spatial diffusion of H atoms in the H_{2} films, D^{d}=5(2)×10^{-17}  cm^{2} s^{-1}, which was 2 orders of ... ...

    Abstract We report on a direct measurement of the quantum diffusion of H atoms in solid molecular hydrogen films at T=0.7  K. We obtained a rate of pure spatial diffusion of H atoms in the H_{2} films, D^{d}=5(2)×10^{-17}  cm^{2} s^{-1}, which was 2 orders of magnitude faster than that obtained from H atom recombination, the quantity used in all previous work to characterize the mobility of H atoms in solid H_{2}. We also observed that the H-atom diffusion was significantly enhanced by injection of phonons. Our results provide the first measurement of the pure spatial diffusion rate for H atoms in solid H_{2}, the only solid state system beside ^{3}He-^{4}He mixtures, where atomic diffusion does not vanish even at temperatures below 1 K.
    Language English
    Publishing date 2021-05-28
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.126.195301
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Experimental cell with a Fabry-Pérot resonator tuned in situ for magnetic resonance studies of matrix-isolated radicals at temperatures below 1 K.

    Sheludiakov, S / Lee, D M / Khmelenko, V V / Järvinen, J / Ahokas, J / Vasiliev, S

    The Review of scientific instruments

    2020  Volume 91, Issue 6, Page(s) 63901

    Abstract: We describe the design and construction of an experimental cell for the study of free radicals in macroscopically thick films of solidified molecular and rare gases by 128 GHz Electron Spin Resonance (ESR) at temperatures below 1 K. The ESR resonator has ...

    Abstract We describe the design and construction of an experimental cell for the study of free radicals in macroscopically thick films of solidified molecular and rare gases by 128 GHz Electron Spin Resonance (ESR) at temperatures below 1 K. The ESR resonator has an open Fabry-Pérot design, and its frequency can be tuned in situ by adjusting the spacing between the mirrors. The tuning mechanism consists of a piezo positioner and a stainless-steel edge-welded bellows, which can change the resonator frequency by at least 6 GHz. The films of solidified gases can be deposited either directly from a room temperature reservoir or by recondensing from a specially arranged chamber. The free radicals can be created in the solid films by dissociating matrix species by running an rf discharge in a helium vapor. We suggest that such a sample cell design can also be used for a broad range of low-temperature ESR experiments where sample cooling needs to be enhanced by the presence of superfluid helium.
    Language English
    Publishing date 2020-06-17
    Publishing country United States
    Document type Journal Article
    ZDB-ID 209865-9
    ISSN 1089-7623 ; 0034-6748
    ISSN (online) 1089-7623
    ISSN 0034-6748
    DOI 10.1063/5.0012178
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Dynamic nuclear polarization and ESR hole burning in As doped silicon.

    Järvinen, J / Zvezdov, D / Ahokas, J / Sheludiakov, S / Lehtonen, L / Vasiliev, S / Vlasenko, L / Ishikawa, Y / Fujii, Y

    Physical chemistry chemical physics : PCCP

    2020  Volume 22, Issue 18, Page(s) 10227–10237

    Abstract: We present an experimental study of the Dynamic Nuclear Polarization (DNP) ... ...

    Abstract We present an experimental study of the Dynamic Nuclear Polarization (DNP) of
    Language English
    Publishing date 2020-04-30
    Publishing country England
    Document type Journal Article
    ZDB-ID 1476244-4
    ISSN 1463-9084 ; 1463-9076
    ISSN (online) 1463-9084
    ISSN 1463-9076
    DOI 10.1039/c9cp06859g
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Formation of Nuclear-Polarized Phases of H Atoms Embedded in Solid H_{2} Films.

    Sheludiakov, S / McColgan, P T / Lee, D M / Khmelenko, V V / Järvinen, J / Ahokas, J / Vasiliev, S

    Physical review letters

    2019  Volume 122, Issue 22, Page(s) 225301

    Abstract: We report on an experimental observation of two phases of hydrogen atoms in solid H_{2} films at temperatures of 0.1-0.8 K, characterized by a large enhancement of the nuclear spin polarization compared to that given by Boltzmann statistics (p=0.15 at T= ... ...

    Abstract We report on an experimental observation of two phases of hydrogen atoms in solid H_{2} films at temperatures of 0.1-0.8 K, characterized by a large enhancement of the nuclear spin polarization compared to that given by Boltzmann statistics (p=0.15 at T=0.15  K). The first phase with p=0.35(5) is formed spontaneously during sample storage in a high magnetic field (B=4.6  T). The second phase with an even higher nuclear polarization, p=0.75(7), can be achieved at T≤0.55  K by repeating sequences of dynamic nuclear polarization followed by a system relaxation. Upon warming through the range 0.55-0.65 K, the highly nuclear-polarized phase undergoes a phase transition to the spontaneously polarized phase which breaks down at T≃0.8  K, and the nuclear polarization gradually converges to the Boltzmann distribution. We discuss possible scenarios for explaining the nature of the observed phenomena.
    Language English
    Publishing date 2019-07-08
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.122.225301
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  5. Article ; Online: ESR study of atomic hydrogen and tritium in solid T

    Sheludiakov, S / Ahokas, J / Järvinen, J / Lehtonen, L / Vainio, O / Vasiliev, S / Lee, D M / Khmelenko, V V

    Physical chemistry chemical physics : PCCP

    2017  Volume 19, Issue 4, Page(s) 2834–2842

    Abstract: We report on the first ESR study of atomic hydrogen and tritium stabilized in solid ... ...

    Abstract We report on the first ESR study of atomic hydrogen and tritium stabilized in solid T
    Language English
    Publishing date 2017-01-25
    Publishing country England
    Document type Journal Article
    ZDB-ID 1476244-4
    ISSN 1463-9084 ; 1463-9076
    ISSN (online) 1463-9084
    ISSN 1463-9076
    DOI 10.1039/c6cp06933a
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Tunneling chemical exchange reaction D + HD → D

    Sheludiakov, S / Ahokas, J / Järvinen, J / Zvezdov, D / Lehtonen, L / Vainio, O / Vasiliev, S / Lee, D M / Khmelenko, V V

    Physical chemistry chemical physics : PCCP

    2016  Volume 18, Issue 42, Page(s) 29600–29606

    Abstract: We report on a study of the exchange tunneling reaction D + HD → ... ...

    Abstract We report on a study of the exchange tunneling reaction D + HD → D
    Language English
    Publishing date 2016-10-26
    Publishing country England
    Document type Journal Article
    ZDB-ID 1476244-4
    ISSN 1463-9084 ; 1463-9076
    ISSN (online) 1463-9084
    ISSN 1463-9076
    DOI 10.1039/c6cp05486b
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article ; Online: Experimental cell for molecular beam deposition and magnetic resonance studies of matrix isolated radicals at temperatures below 1 K.

    Sheludiakov, S / Ahokas, J / Vainio, O / Järvinen, J / Zvezdov, D / Vasiliev, S / Khmelenko, V V / Mao, S / Lee, D M

    The Review of scientific instruments

    2014  Volume 85, Issue 5, Page(s) 53902

    Abstract: We present the design and performance of an experimental cell constructed for matrix isolation studies of H and D atoms in solid H2/D2 films, which are created by molecular beam deposition at temperatures below 1 K. The sample cell allows sensitive ... ...

    Abstract We present the design and performance of an experimental cell constructed for matrix isolation studies of H and D atoms in solid H2/D2 films, which are created by molecular beam deposition at temperatures below 1 K. The sample cell allows sensitive weighing of the films by a quartz microbalance (QM) and their studies by magnetic resonance techniques in a strong magnetic field of 4.6 T. We are able to regulate the deposition rate in the range from 0.01 to 10 molecular layers/s, and measure the thickness with ≈0.2 monolayer resolution. The upper QM electrode serves as a mirror for a 128 GHz Fabry-Perot resonator connected to an electron spin resonance (ESR) spectrometer. H and D atoms were created by RF discharge in situ in the sample cell, and characterized by ESR and electron-nuclear double resonance. From the magnetic resonance measurements we conclude that the films are smooth and provide homogeneous trapping conditions for embedded atoms. The current sample cell design also makes it possible to calibrate the ESR signal and estimate the average and local concentrations of H and D radicals in the film.
    Language English
    Publishing date 2014-05
    Publishing country United States
    Document type Journal Article
    ZDB-ID 209865-9
    ISSN 1089-7623 ; 0034-6748
    ISSN (online) 1089-7623
    ISSN 0034-6748
    DOI 10.1063/1.4875985
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article ; Online: Bose-Einstein condensation of magnons in atomic hydrogen gas.

    Vainio, O / Ahokas, J / Järvinen, J / Lehtonen, L / Novotny, S / Sheludiakov, S / Suominen, K-A / Vasiliev, S / Zvezdov, D / Khmelenko, V V / Lee, D M

    Physical review letters

    2015  Volume 114, Issue 12, Page(s) 125304

    Abstract: We report on experimental observation of Bose-Einstein condensation (BEC)-like behavior of quantized electron spin waves (magnons) in a dense gas of spin-polarized atomic hydrogen. The magnons are trapped and controlled with inhomogeneous magnetic fields ...

    Abstract We report on experimental observation of Bose-Einstein condensation (BEC)-like behavior of quantized electron spin waves (magnons) in a dense gas of spin-polarized atomic hydrogen. The magnons are trapped and controlled with inhomogeneous magnetic fields and described by a Schrödinger-like wave equation, in analogy to the BEC experiments with neutral atoms. We have observed the appearance of a sharp feature in the ESR spectrum displaced from the normal spin wave spectrum. We believe that this observation corresponds to a sudden growth of the ground-state population of the magnons and emergence of their spontaneous coherence for hydrogen gas densities exceeding a critical value, dependent on the trapping potential. We interpret the results as a BEC of nonequilibrium magnons which were formed by applying the rf power.
    Language English
    Publishing date 2015-03-27
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.114.125304
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  9. Article ; Online: Dynamic nuclear polarization of high-density atomic hydrogen in solid mixtures of molecular hydrogen isotopes.

    Sheludiakov, S / Ahokas, J / Järvinen, J / Zvezdov, D / Vainio, O / Lehtonen, L / Vasiliev, S / Mao, S / Khmelenko, V V / Lee, D M

    Physical review letters

    2014  Volume 113, Issue 26, Page(s) 265303

    Abstract: We report on magnetic resonance studies of high-density atomic hydrogen and deuterium in solid hydrogen matrices at temperatures below 1 K. Average concentrations of H atoms ≈3×10(19)  cm(-3) are obtained in chemical tunneling reactions of isotope ... ...

    Abstract We report on magnetic resonance studies of high-density atomic hydrogen and deuterium in solid hydrogen matrices at temperatures below 1 K. Average concentrations of H atoms ≈3×10(19)  cm(-3) are obtained in chemical tunneling reactions of isotope exchange with D atoms. The products of these reactions are closely located pairs of H atoms near D2 molecules with strong exchange interactions. We discovered a dynamic nuclear polarization effect on H atoms created by pumping the center of the H electron spin resonance spectrum, similar to the Overhauser effect in metals. Our results indicate that H atoms may be arranged inside molecular matrices at separations equivalent to local concentrations of 2.6×10(21)  cm(-3). This opens up a way to build a metallic state of atomic hydrogen at zero pressure.
    Language English
    Publishing date 2014-12-31
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.113.265303
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