WETTING STUDIES OF LIQUID-HE-4 ON VARIOUS CS SURFACES

Cesium is a surface not wetted by liquid He-4 below a certain temperat ure, T-w approximate to 2K. However, one observes that a thick helium pm remains on the Cs substrate even if the surface is cooled below T-w from the wetted state. This leaves the question how the system will f inally evolve from this metastable state to the thermodynamic equilibr ium, represented by a microscopically thin film. We investigate the dy namic and static behavioar of dewetting 4He films on cesiated surfaces . Space and time resolved measurements of the thickness of the helium film are performed using a surface plasmon microscope. We have measure d the work function of pure and oxidized Gs via photo current spectros copy.