Abstract:
Acoustic cavitation results in extraordinary transient conditions inside the collapsing bubble. In addition to interesting chemical effects (sonochemistry), cavitation also produces light emission. Such sonoluminescence from cavitating clouds of bubbles (``multibubble sonoluminescence,'' MBSL) in room temperature liquids closely resemble flame emission, and this has been used to measure the effective temperature and pressure of species formed during cavitation. Effective emission temperatures have been obtained for MBSL from both excited state C[inf 2] emission (from sonolysis of hydrocarbons and silicone oil) and from excited state metal atom emission (from sonolysis of several volatile metal carbonyls). Effective pressures can be obtained from line broadening and line shifts of the metal atom emission. The effective transient conditions formed during cavitation of bubble clouds are ~5000 K, ~1700 atm, which implies heating and cooling rates in excess of 10[sup 10] K/s. Temperatures reached during single bubble sonoluminescence (SBSL) are likely to be very much higher. Differences between MBSL and SBSL will be discussed. The chemistry generated by cavitation hot spots often differs from either ordinary thermal or photochemical processes, and sonochemistry represents a fundamentally unique interaction of energy and matter. [Work supported by NSF.]