Picosecond sonoluminescence from macroscopic to microscopic models

Abstract

The discovery of stable ‘‘picosecond’’ sonoluminescence (SL) has stimulated a great deal of theoretical effort aimed at explaining this striking result. Instead of assuming a perfectly smooth spherical bubble (as in the hot-spot theory, the converging shock-wave model or the Casimir effect model), our model is based on bubble deformation and the subsequent disruption of the interface toward the end of the collapse. The formation of an intracavity spray via the Taylor (hydrodynamic) or the Rayleigh (electrohydrodynamic) instabilities and the electrification of the tiny droplets due to the disturbances of the interfacial electrical double layer during the spraying process are described. The high electrical field (E≂109 Vm−1) characterizing a small area of a droplet surface is considered to be responsible for the field emission process. The formation and expansion of a dense microplasma inside the cavity as a consequence of the emission of electrons is proposed to be the origin of picosecond sonoluminescence. By means of this model, which is based both on hydrodynamics and on the microstructure of the bubble interface, the main experimental observations (SL flash temporal localization and duration, shape of the SL spectrum) can be explained.

Nature of the “Extreme Conditions” in Single Sonoluminescing Bubbles

“…In this sense, it affords a supplementary constraint on any attempt to model sonoluminescence. However, our analysis renews interest in a hypothesis that two of us reported at the 128th meeting of the Acoustical Society of America (manuscript in preparation) . According to this hypothesis, the injection of electrified droplets via the nonradial oscillations of a collapsing bubble could lead to the formation of a hot intracavity plasma with the properties of high-energy sparks triggered off under high pressure.…”