Equilibrium thickness of saturated superfluid He-3 films on a copper substrate

Much theoretical interest focuses on the equilibrium thickness of liquid he lium films adsorbed onto a substrate. To address this issue in liquid He-3, an experiment to measure the thickness d of a saturated superfluid He-3 fi lm, on a horizontal copper substrate which is a height h above the free sur face of the liquid bath, was carried out. The free surface of the bulk supe rfluid He-3 is slowly lowered, thus increasing h, by expanding a bellows (a ctuated with superfluid He-4) at the base of the cell. While doing this, co ntinuous measurements of the thickness of the superfluid 3He film, from whi ch we can obtain nth), are made. These measurements then allow us to extrac t information on the attractive (van der Waals) potential between the super fluid He-3 film and the copper substrate. (C) 2000 Elsevier Science B.V. Al l rights reserved.