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Etude des propriétés de mouillage de l'hélium sur des métaux alcalins

Abstract : This thesis presents an experimental study of the wetting transition of liquid helium on the surface of metallic cesium and a determination of the prewetting line of this liquid on rubidium surface. First, we recall Cheng's et al. criterion for the wetting of a surface by liquid helium at zero temperature and also its extension for non zero temperatures which determines the wetting temperature and the prewetting line. An improvement of this model is proposed which takes into account the temperature dependence of various parameters. The experimental methods are original on two points: the wetting of a surface is monitored through thermal conductivity of the sample making use of the relation between the superfluidity of the film at low temperature and its thickness; the studied surfaces are those of bulk metal kept in sealed cells. The wetting transition on cesium was observed. It was found to be continuous and hysteretic. A desaturation technique has been developped which allows to observe the prewetting transition on the same rubidium surface at various temperatures. The prewetting line is determined experimentally between 1 and 1.7 kelvins. It suggests that rubidium is only slightly wetted at zero temperature. Finally, it is shown that a limited oxidization of a rubidium surface makes it less wettable by helium. For the first time, we have observed a dry rubidium surface at saturation and along with a dewetting transition onto this surface.
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  • HAL Id : tel-00011904, version 1


Benoit Demolder. Etude des propriétés de mouillage de l'hélium sur des métaux alcalins. Matière Condensée [cond-mat]. Université Pierre et Marie Curie - Paris VI, 1996. Français. ⟨tel-00011904⟩



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