Lab. de Sonochimie et d'Etude de la Cavitation, Inst. Meurice, 1, Av. E. Gryzon, 1070 Brussels, Belgium
Ecole Superieure d'Electricite, 1192 Gif-sur-Yvette Cedex, France
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(congruent to)10[sup 9] Vm[sup -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.