The Shock-Wave Theory of Sonoluminescence
When driven into violent pulsation by a sufficiently strong source of sound, a bubble of air in water emits light, a phenomenon known as ‘sonoluminescence’. The reasons for this are not yet fully understood. The most popular explanation at this time is the shock-wave theory of sonoluminescence. This supposes that, because the bubble surface moves inwards supersonically with respect to the air in the bubble during the compressive parts of the acoustic cycle, it launches an imploding spherical shock wave that becomes so strong, as it focuses at the center of the bubble, that it ionizes the air, the observed light being emitted from the resulting plasma ball. We discuss here the structure and stability of spherical shocks in ideal and van der Waals gases, paying particular attention to similarity shocks of the Guderley type and their relevance to sonoluminescence. We discuss the status of the shock-wave theory of sonoluminescence and alternative explanations. We pose a number of theoretical challenges.
KeywordsEntropy Argon Compressibility Xenon Acoustics
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