PHYSICAL ASPECTS OF SONOLUMINESCENCE FROM ACOUSTIC CAVITATION

The passage ultrasonic wave through a medium can sometimes result in t he production of acoustic cavitation which is often accompanied by the generation of light; a process known as sonoluminescence or 'light fr om sound'. A brief historical overview of early sonoluminescence (SL) research is presented, followed by a phenomenological description of t he physics of cavitation bubble fields. Many of the published results describing the features of SL (pulse duration, phasing, spectra, etc.) are inconsistent and sometimes contradictory. However, recent studies of sonoluminescence from individual, radially pulsating bubbles draw a consistent picture. Single-bubble SL flashes occur once every acoust ic cycle and coincide precisely with bubble collapse. The duration of the flash is believed to be less than or equal to 50 ps and the missio n spectra indicate substantial heating of the bubble interior. These r esults suggest that the primary mechanism for single-bubble sonolumine scence is the rapid heating of the interior of the collapsing bubble.