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Research output: Contribution to Journal/Magazine › Conference article › peer-review
Research output: Contribution to Journal/Magazine › Conference article › peer-review
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TY - JOUR
T1 - Neutron reflection from the surface of a liquid 4He- 3He mixture
AU - Kirichek, O.
AU - Vasilev, N. D.
AU - Charlton, T. R.
AU - Kinane, C. J.
AU - Dalgliesh, R. M.
AU - Ganshin, A.
AU - Langridge, S.
AU - McClintock, P. V.E.
PY - 2012/1/1
Y1 - 2012/1/1
N2 - We have used neutron reflection from the liquid surface at ultra-low temperatures to study the surface properties of liquid helium. We measured neutron scattering from the free surfaces of commercially pure 4He (0.3 ppm of 3He impurities) and of a 3He-4He mixture with a 3He concentration of 0.5% for temperatures in the range from 340mK to 2.2K We compare the reflected neutron intensity for different temperatures and we fit a model that describes the collected data. The data are described well by a diffusive 3He layer of a few hundred Angstrom thickness on the bulk 4He liquid surface. Even at high temperatures (∼2K) there is an increased concentration of 3He atoms near the liquid surface. The distribution does not change very much with temperature. At low temperatures the neutron absorption increases significantly, which might be an indication of the formation of Andreev states. However, the shapes of the curves do not change very much which seems to suggest that the layer formed by the 3He atoms in Andreev states is very thin ∼ 10Å. The experimental method, based on neutron reflectometry, opens up new opportunities for the study of the surfaces and interfaces of quantum fluids and solids.
AB - We have used neutron reflection from the liquid surface at ultra-low temperatures to study the surface properties of liquid helium. We measured neutron scattering from the free surfaces of commercially pure 4He (0.3 ppm of 3He impurities) and of a 3He-4He mixture with a 3He concentration of 0.5% for temperatures in the range from 340mK to 2.2K We compare the reflected neutron intensity for different temperatures and we fit a model that describes the collected data. The data are described well by a diffusive 3He layer of a few hundred Angstrom thickness on the bulk 4He liquid surface. Even at high temperatures (∼2K) there is an increased concentration of 3He atoms near the liquid surface. The distribution does not change very much with temperature. At low temperatures the neutron absorption increases significantly, which might be an indication of the formation of Andreev states. However, the shapes of the curves do not change very much which seems to suggest that the layer formed by the 3He atoms in Andreev states is very thin ∼ 10Å. The experimental method, based on neutron reflectometry, opens up new opportunities for the study of the surfaces and interfaces of quantum fluids and solids.
U2 - 10.1088/1742-6596/400/1/012033
DO - 10.1088/1742-6596/400/1/012033
M3 - Conference article
AN - SCOPUS:84873632603
VL - 400
JO - Journal of Physics: Conference Series
JF - Journal of Physics: Conference Series
SN - 1742-6588
IS - 1
M1 - 012033
T2 - 26th International Conference on Low Temperature Physics, LT 2011
Y2 - 10 August 2011 through 17 August 2011
ER -