Wetting Phenomena in 3 He- 4 He Mixtures on Weak and Superweak Substrates

Abstract

We explore wetting phenomena in3He-4He mixtures adsorbed on the newly discovered superweak oxidized alkali metal substrates. An approximate description of the relationship between the substrate work function and the substrate adsorbate potential well depth D is given. Within a slab model we derive the wetting phase diagram at liquid-vapor coexistence. On oxidized cesium at T = 0 we obtain the values of D for which triple point dewetting vanishes and for which pure3He ceases to wet. Reduction of D leads to the disappearance of wetting at the substrate-3He interface in an interesting scenario violating the Cahn wetting theorem.