Ellipsometric studies of evaporation and condensation of the helium film

Measurements have been made of the behaviour of the helium film when it is isolated from the bath. The film is measured optically (using an automatic ellipsometer) on a magnetically leviated substrate. Spontaneous evaporation is observed due to the extreme sensitivity of the film to small changes in thermal equilibrium. However, contrary to expectations the evaporation rate is observed to increase as the film thickness decreases. (Auth.)