Density of superfluid helium droplets

Abstract

The classical integral cross sections of large superfluid ${}^{4}{\mathrm{He}}_{N}$ droplets and the number of atoms in the droplets ${(N=10}^{3}\ensuremath{-}{10}^{4})$ have been measured in molecular beam scattering experiments. These measurements are in good agreement with the cross sections predicted from density functional calculations of the radial density distributions. By using a simple model for the density profile a 10--90 % surface thickness of about 6--8 \AA{} is extracted directly from the data.