Scaling the superfluid density of 4 he confined in planar geometry

We have measured the superfluid density of ⁴He confined between two silicon surfaces. The reduction of ρ{variant}_s from the bulk value near the transition is observed for 0.106, 0.519, 2.8 and 3.9 μm confinement spacings,L. We find that the systematic reduction of p., with confinement do not scale with the bulk correlation length, ξ. We find that the data scale with L, but not with the temperature dependence of ξ We report. calculations of ρ{variant}_s within Ψ theory which include van der Waals effects. We also report analysis according to a suggesttion by Privman.