Phonon Excitations in Liquid He II

Abstract

Recent experimental data on He II have been analyzed in order to test various analytic properties of the phonon dispersion curve. In particular ${[\frac{\ensuremath{\epsilon}(p)}{p}]}^{2}$, where $\ensuremath{\epsilon}(p)$ is the energy of an elementary excitation, seems to be well represented by a power expansion in $p$ up to $p=2.6$ ${\mathrm{\AA{}}}^{\ensuremath{-}1}$.