A1 Refereed original research article in a scientific journal
Formation of Nuclear-Polarized Phases of H Atoms Embedded in Solid H-2 Films
Authors: Sheludiakov S, McColgan PT, Lee DM, Khmelenko VV, Järvinen J, Ahokas J, Vasiliev S
Publisher: AMER PHYSICAL SOC
Publication year: 2019
Journal: Physical Review Letters
Journal name in source: PHYSICAL REVIEW LETTERS
Journal acronym: PHYS REV LETT
Article number: ARTN 225301
Volume: 122
Issue: 22
Number of pages: 5
ISSN: 0031-9007
eISSN: 1079-7114
DOI: https://doi.org/10.1103/PhysRevLett.122.225301(external)
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/41276084(external)
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 similar or equal to 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.
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