Spectrally resolved sonoluminescence as a probe of cavitation

The collapse of bubbles during acoustic cavitation in liquids generates intense local heating, either by adiabatic compression or through shock wave formation. We have been able to quantify local temperatures by spectroscopic analysis of Sonoluminescence from cavitating bubble clouds. Sonoluminescence in hydrocarbon liquids closely reassembles flame emission. From hydrocarbons or silicone oil, emission from excited states of diatomic carbon, C₂, are observed; the rotational and vibrational fine structure of this emission permits a spectroscopic determination of the emission temperature of the excited states of C₂, which is ≈51.00 K. Sonoluminescence from excited state metal atoms is produced during sonolysis of volatile metal carbonyls. Linewidth analysis of this emission permits us to determine collisional lifetimes of the emitting atoms and hence to estimate effective local pressures during cavitation. The calculated pressure experienced by Cr atoms during emission from Cr(CO)₆ is 1700 atmospheres (1.72 kBar)