Sonoluminescence and sonochemistry

The chemical effects of ultrasound originate from acoustic cavitation, which produces extremely energetic local transient conditions. In cavitating clouds of bubbles, both sonochemistry and sonoluminescence occur. Spectroscopic analysis of sonoluminescence from hydrocarbons and from metal carbonyls reveal temperatures of approximately 5000 K, approximately 1000 atm, with heating and cooling rates that exceed 10¹⁰ K/s. Single bubble sonoluminescence produces much more symmetric bubble collapse with subsequently much higher effective temperatures during collapse. In cold liquids, bubble cloud cavitation is able to drive reactions that normally occur only under extreme conditions. Examples include activation of liquid-solid reactions and synthesis of amorphous and nanophase metals, and the synthesis of novel biomaterials, especially protein microspheres. Another remarkable phenomena occurs during ultrasonic irradiation of liquid-solid slurries: extremely high speed inter-particle collisions occur from cavitational shock waves at roughly half the speed of sound with effective temperatures of approximately 3000 K at the point of impact.