Incomplete wetting of helium i on copper

Abstract

Capacitance measurements have shown that liquid helium exhibits reduced wetting on copper surfaces above the λ point, as compared to superfluid helium. Particular care was taken to ensure an isothermal environment, including the use of an experimental cell entirely surrounded by superfluid. Experiments on the wetting of ${}_{}{}^3{}_{}{}^{}\mathrm{-}_{}^4{}_{}{}^{}$He mixtures of various concentrations show a wetting transition at the λ point of the mixture film. The thick-film–thin-film transition requires an anomalously long time of order 10 h to go to completion unless stabilized by a favorable temperature gradient.