BUBBLE SHAPE OSCILLATIONS AND THE ONSET OF SONOLUMINESCENCE

An air bubble trapped in water by an oscillating acoustic field underg oes either spherical or nonspherical pulsations depending on the stren gth of the forcing pressure. Two different instability mechanisms (the Rayleigh-Taylor instability and parametric instability) cause deviati ons from sphericity. Distinguishing these mechanisms allows an explana tion of many features of recent experiments on single bubble sonolumin escence, and suggests methods for finding sonoluminescence in differen t parameter regimes.