Third-sound studies inHe3-He4films

Abstract

We report the results of measurements of the velocity and damping of third sound in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-${}_{}{}^4{}_{}{}^{}\mathrm{He}$ mixture films for $T<\mathrm{}0.3\mathrm{}$ K and for ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ coverages up to about two monolayers. The velocity measurements do not show the coverage-dependent behavior seen by Laheurte et al. and are consistent with earlier less-precise results at higher temperature and coverages which suggest a situation of nearly complete isotopic layering. The damping measurements show interesting and unexplained structure.