QFS 2016 Book of Abstracts

Abstracts

P4.32 Magnetic resonance study of high-density atomic hydrogen and tritium stabilized in solid tritium matrices below 1K Sheludiakov Sergei(1), Ahokas Janne(1), J¨arvinen Jarno(1), Vainio Otto(1), Lehtonen Lauri(1), Zvezdov Denis(1,2) Vasiliev Sergey(1), Khmelenko Vladimir V.(3), Lee David M.(3) 1) University of Turku, Faculty of Mathematics and Natural Science, Department of Physics and Astronomy, 20014 Turku, Finland 2) Kazan Federal University, Institute of Physics, 18 Kremlyovskaya St., Kazan 42008, Republic of Tatarstan, Russia 3) Texas A&M University, College of Science, Department of Physics and Astronomy, College Station, TX 77843, USA We report on a magnetic resonance study of high-density atomic hydrogen and tritium stabilized in a pure T 2 and T 2 : H 2 matrices below 1K. Average concentrations of T atoms exceeding 1 . 5 × 10 20 cm − 3 were obtained while storing thin (50-500nm) tritium films at temperature 150mK. The record-high concentration of H atoms, 9 × 10 19 cm − 3 , was reached by storing T 2 : H 2 mixtures where a fraction of T atoms becomes converted into H due to the isotopic exchange reaction T + H 2 = TH + H . The maximum concentrations of H and T atoms were limited by their recombination which occurred in an explosive manner while the threshold concentrations were found to be dependent both on the film thickness and storage temperature. P4.33 Elastic measurements of TLSs in amorphous silicon at mK temperatures A. Fefferman 1 , A. Maldonado-Cid 1 , E. Collin 1 , X. Liu 2 , T. Metcalf 2 , G. Jernigan 2 1) Institut N´eel/CNRS and Universit´e Grenoble Alpes, 38042 Grenoble, France 2) US Naval Research Laboratory, SW Washington, DC 20375, USA The low temperature properties of glass are distinct from those of crystals due to the presence of poorly understood low-energy excitations. These are usually thought to be atoms tunneling between nearby equilibria, forming tunneling two level systems (TLSs). Elastic measurements on amorphous silicon films deposited with e-beam evaporation suggest that this material contains a variable density of TLSs that decreases as the growth temperature increases from room temperature to 400 o C. We present measurements of the elastic properties of these films down to 10 mK and an analysis in the framework of the standard tunneling model.

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