Single Bubble Sonochemistry

Abstract

Until recently, SL has often been studied in the case of inertial (transient) cavitation [1.2] although a correlation ‘SL/bubble dynamics’ has been difficult and relatively inaccurate. These drawbacks -associated with multi-bubble fields- are due to the fact that, under these conditions, bubbles of different sizes are loosely coupled and their growth and collapse are somewhat random. Most interesting are the recent findings on single bubbles maintained in levitation in a resonant acoustic set-up [3] -an acoustic energy concentration factor equal to ~11 orders of magnitude [4], the shortness of the SL flash [4,5] (<50ps), the clock-like emission [4], the appearence of the flash within 500 ps near maximum collapse, the sensitivity to noble gases [6] and the non-sphericity of the bubble at the time of emission [7]. This considerable progress in the knowledge of SL is due to the fact that single bubbles constitute very controllable systems [8]. Up to now, the sonochemical activity of cavitating media [9,10,11] has only been described in the case of multi-bubble clouds (stable [12] and inertial cavitation; aqueous and organic [13,14] solutions). We report here that single bubbles in levitation are also chemically active. A dosimetry is reported in the case of Weissler’s system. The interest to use chemical species as tracers for the investigations of liquid flow around single bubbles will be reported with more details elsewhere.