Neutron reflection from a liquid helium surface.

Authors :: Charlton, T. R.
Dalgliesh, R. M.
Kirichek, O.
Langridge, S.
Ganshin, A.
McClintock, P. V. E.
Source :: Low Temperature Physics; Apr2008, Vol. 34 Issue 4/5, p316-319, 4p, 1 Diagram, 3 Graphs
Publication Year :: 2008
Abstract: The reflection of neutrons from a helium surface is observed for the first time. The <superscript>4</superscript>He surface is smoother in the superfluid state at 1.54 K than in the case of the normal liquid at 2.3 K. In the superfluid state we also observe a surface layer ∼200 Å thick which has a subtly different neutron scattering cross section, which may be explained by an enhanced Bose-Einstein condensate fraction close to the helium surface. The application of neutron reflectometry described in this paper creates new and exciting opportunities for the surface and interfacial study of quantum fluids. [ABSTRACT FROM AUTHOR]