J. Phys. IV France 10 (2000) Pr7-177-Pr7-180
Dynamics of liquid 4He in Gel-TekO. Plantevin1, B. Fåk1 and H.R. Glyde2
1 Département de Recherche Fondamentale sur la Matière Condensée, SPSMS/MDN, CEA Grenoble, 38054 Grenoble cedex 9, France
2 Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, U.S.A.
We have studied the excitations in superfluid 4He in a new porous silica medium : Gel-Tek. This material has a pore size of 25 Å and a very high specific surface area. We have measured the dynamical structure factor of liquid 4He confined in Gel-Tek using inelastic neutron scattering, for several filling fractions between 56% and 105% and several temperatures between 50 mK and 2.5 K. We have observed new features compared to bulk liquid 4He. We measured in particular a broad component involving approximately 40% of the helium atoms above the first inert layer. This component appears to be temperature independent between 50 mK and 2.5 K. For filling fractions larger than 55% above the layer, we have observed a maxon-roton type excitation. We have also detected additional intensity at energies below the roton, which we attributed to 2-dimensional excitations propagating in the liquid near the walls of the substrate. We give here a qualitative overview of these different features.
© EDP Sciences 2000