2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/143604The reflection of neutrons from a helium surface has been observed for the first time. The 4He 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 Angstroms 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.to be published in Low Temperature PhysicsSoft Condensed MatterOther Condensed Mattertext