Extreme conditions during multibubble cavitation: Sono luminescence as a spectroscopic probe

We review recent work on the use of sonoluminescence (SL) to probe spectroscopically the conditions created during cavitation, both in clouds of collapsing bubbles (multibubble sonoluminescence, (MBSL)) and in single bubble events. The effective MBSL temperature can be controlled by the vapor pressure of the liquid or the thermal conductivity of the dissolved gas over a range from similar to 1600 to similar to 9000 K. The effective pressure during MBSL is similar to 300 bar, based on atomic line shifts. Given nanosecond emission times, this means that cooling rates are >10(12) K/s. In sulfuric and phosphoric acid, the low volatility and high solubility of any sonolysis products make bubble collapse more efficient and evidence for an optically opaque plasma core is found. (C) 2011 Elsevier B.V. All rights reserved.