OSCILLATION OF A BUBBLE IN SUPERFLUID HELIUM.

Abstract

The properties of bubble formation at the surface of a thin metal film immersed in He II have been investigated. The bubbles are created using a focused laser spot as a localized heat source. Two distinct stages of bubble formation are observed as the power density is increased. Both of these stages exhibit well defined oscillatory behavior. The two stages are identified by different threshold powers, frequency spectra and optical properties. In addition, the fundamental frequency of the first stage increased with increasing power density while the opposite is true for the second stage. The second stage has been identified as a vapor bubble and the oscillation is associated with a natural resonant frequency predicted by classical theory. At the present time it is not apparent whether the first stage is related to a thin layer of normal helium or a thin vapor pocket.