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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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