Structure and Modes of a Superfluid Atmosphere

A theory of the structure, energetics, and modes of a film formed from a non-self-bound fluid is developed and applied to spin-polarized hydrogen at zero temperature. A hydrogen film is found to saturate at areal density ${n_s}^{\mathrm{sat}}=1.1\mathrm{}\times {10}^{14}$ ${\mathrm{cm}}^{-2\mathrm{}}$ and to support a third-sound mode with velocity that varies strongly with areal density.