CONFINEMENT EFFECTS ON SUPERFLUID-HELIUM

Inelastic neutron scattering has been used to probe the collective exc itations of superfluid helium confined to silica aerogel. Confinement in porous aerogel results in a crossover behavior in the temperature d ependence of the roton where the energy is relatively temperature inde pendent below 1.9 K and strongly temperature dependent above 1.9 K. As in the bulk liquid the relationship between the microscopic excitatio n spectrum and the macroscopic thermodynamics of the confined system a re found to be in good agreement.