SOME COMMENTS ON HELIUM FILMS

Abstract

The Polanyi potential theory is applied to the helium film and leads to a qualitative understanding of the high density of the first few layers and the differential entropy. Between 1.75°K. and the λ-point the film may consist of an inner solid portion, an intermediate portion of helium I, and an outer portion of helium II. For thick films the variation of zero-point energy with thickness must be considered. The zero-point energy of the Debye waves is shown to be important at film thicknesses of the order of 4 × 10⁻⁶ cm. The effect of heat radiation incident upon the film is considered.