SURFACE OXIDE LAYERS AND THE WETTING TEMPERATURE OF ALKALI-METALS

It is now well known that at low temperatures liquid helium does not w et unoxidised caesium and rubidium surfaces. Recent experiments on rub idium have shown tile unexpected result that its wetting temperature i s considerably increased by a small amount of oxidation and it was sug gested that this corresponds to a decrease in the electronic work func tion. We propose an idealised model for the interaction of helium with the surface of an oxidised alkali metal and find that it predicts tha t such a surface could indeed have a higher wetting temperature than t he pure metal.